Improved 3D form profiler based on extending illumination aperture

Mostafa Agour; Claas Falldorf; Ralf B. Bergmann

doi:10.1117/12.2673783

15 August 2023 Improved 3D form profiler based on extending illumination aperture

Mostafa Agour, Claas Falldorf, Ralf B. Bergmann

Proceedings Volume 12618, Optical Measurement Systems for Industrial Inspection XIII; 126180T (2023) https://doi.org/10.1117/12.2673783
Event: SPIE Optical Metrology, 2023, Munich, Germany

Abstract

We recently demonstrated that the 3D shape of micro-parts can be measured using LED illumination based on contrast evaluation. The technique is based on imaging the object under test using partially coherent illumination. The limited spatial coherence of LED illumination was utilized to discriminate depth. For a fast depth scan without mechanically moving parts, an electrically tunable lens (ETL) in a 4f optical configuration is used. This approach is efficient, takes less than a second to capture all required images, is eye-safe, and offers a depth of focus of a few millimeters. However, the main limitation of the proposed approach arises from the underlying assumption that a small angle of variation of illumination is required. Such a small illumination aperture affects the axial scan resolution that dominates the measurement uncertainty. In the present paper we propose a method to overcome the main limitation of the above-mentioned profiling technique. The approach combines measurements with multiple illumination directions achieved by illuminating the object simultaneously with several independent light sources. In this way, the full-width half maximum of the contrast envelope is reduced. A tilted metallic plate is used for proof of concept.

Conference Presentation

Citation Download Citation

Mostafa Agour, Claas Falldorf, and Ralf B. Bergmann "Improved 3D form profiler based on extending illumination aperture", Proc. SPIE 12618, Optical Measurement Systems for Industrial Inspection XIII, 126180T (15 August 2023); https://doi.org/10.1117/12.2673783

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