Interferometer for optical waviness and figure testing

Klaus R. Freischlad

doi:10.1117/12.281208

17 September 1997 Interferometer for optical waviness and figure testing

Klaus R. Freischlad

Proceedings Volume 3098, Optical Inspection and Micromeasurements II; (1997) https://doi.org/10.1117/12.281208
Event: Lasers and Optics in Manufacturing III, 1997, Munich, Germany

Abstract

A novel instrument is described for the optical, non-contact measurement of the waviness and figure component of the surface texture of flat surface. Here the spatial frequency range for waviness is typically chosen from 1.25/mm to 0.05/mm, whereas the global figure error contains the lower spatial frequencies. The special requirements on the dynamic range, the spatial resolution, and the signal-to-noise ratio of the measurement are discussed. The presented instrument consists of a white-light, extended-source, phase-shifting Mach-Zehnder interferometer. The special design employing low temporal and spatial coherence avoids coherent speckle noise on the measured surface maps while providing good spatial resolution. Thus in the waviness frequency band the modulation transfer function exceeds 0.75, an the RMS- precision is 0.1nm over the measurement area of 100mm in diameter. Measurement examples of typical applications, e.g. substrates for hard disks and flat panel displays, are shown.

Citation Download Citation

Klaus R. Freischlad "Interferometer for optical waviness and figure testing", Proc. SPIE 3098, Optical Inspection and Micromeasurements II, (17 September 1997); https://doi.org/10.1117/12.281208

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