3-D sensing with a confocal optical `macroscope'

Gerd Haeusler; Juergen M. Herrmann

doi:10.1117/12.34743

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1 July 1990 3-D sensing with a confocal optical `macroscope'

Gerd Haeusler, Juergen M. Herrmann

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Proceedings Volume 1319, Optics in Complex Systems; (1990) https://doi.org/10.1117/12.34743
Event: 15th International Optics in Complex Systems, 1990, Garmisch, Germany

Abstract

Optical 3D-sensors are useful tools for automatic inspection. But frequently they are complex and expensive. We introduce a simple 'point sensor' for the acquisition of 3D object data, based on a modification of the 'confocal focus sensing'. This principle was described by Shamir et ala, for sensing microscopic, mirrorlike objects. Our modification works for macroscopic objects with rough surfaces. Rough surfaces introduce problems, because, with coherent illumination, we get speckled spot images. To reduce speckle effects,often a very high illumination aperture is used. But when measuring macroscopic objects one needs small apertures to get enough depth of field and to avoid shading. We reduce speckle by using a broadband laser diode or a white light source. Fig.l The sensor works as follows (Fig.l): a light spot is projected onto the object surface. Two images of this light spot are created by the lens L and two beamsplitters. Two pinholes are located on the optical axis, at different distances. The flux l and 2 behind the pinholes is measured. The ratio D1/D2 encodes the object distance. 41/b2 is independent from the object reflectivity.

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Gerd Haeusler and Juergen M. Herrmann "3-D sensing with a confocal optical `macroscope'", Proc. SPIE 1319, Optics in Complex Systems, (1 July 1990); https://doi.org/10.1117/12.34743

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