Absolute shape measurement with coaxial deflectometry: towards interferometric accuracy

Yves Surrel; Maxime Bordoux

doi:10.1117/12.2691658

29 November 2023 Absolute shape measurement with coaxial deflectometry: towards interferometric accuracy

Yves Surrel, Maxime Bordoux

Proceedings Volume 12778, Optifab 2023; 127780Q (2023) https://doi.org/10.1117/12.2691658
Event: SPIE Optifab, 2023, Rochester, New York, United States

Abstract

Deflectometry (shape measurement of a mirror from the distortion of the image of a monitor screen displaying fringes) has been known for a long time, but suffers from intrinsic features that make accurate absolute measurements very difficult. In particular, all the metrological quality depends on the ultra precise identification of the system geometry: ray trajectories in the object space, shape of the monitor screen, position of this screen and position of one point of the measured object, all these in the camera frame of reference. We present an instrument that permits all these identifications in a simple push-button way. The fundamental ambiguity of deflectometry (a single measurement may correspond to an infinite number of object shapes, due to the unknown constant after slopes integration) is raised with our patented coaxial deflectometry approach: two measurements are made with an axial movement of the camera, and only one shape is compatible with these two measurements. We present the identification methodology of the system, and results for absolute measurements of spheres, aspheres and freeforms, within a λ/40 accuracy, with some comparisons with results obtained with a Taylor-Hobson LUPHOScan®.

Conference Presentation

(2023) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

Yves Surrel and Maxime Bordoux "Absolute shape measurement with coaxial deflectometry: towards interferometric accuracy", Proc. SPIE 12778, Optifab 2023, 127780Q (29 November 2023); https://doi.org/10.1117/12.2691658

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