Modelling of the photometric balance for two-wavelength spatially multiplexed digital holography

Matthieu Piniard; Béatrice Sorrente; Gilles Hug; Pascal Picart

doi:10.1117/12.2593719

20 June 2021 Modelling of the photometric balance for two-wavelength spatially multiplexed digital holography

Matthieu Piniard, Béatrice Sorrente, Gilles Hug, Pascal Picart

Proceedings Volume 11783, Modeling Aspects in Optical Metrology VIII; 1178308 (2021) https://doi.org/10.1117/12.2593719
Event: SPIE Optical Metrology, 2021, Online Only

Abstract

Multi-wavelength digital holography is a very powerful approach for surface shape measurements. It has the advantage of being contact-less, non-intrusive, and yields full-field surface shape data without any requirement for scanning. When dealing with off-axis digital holography and spatial multiplexing of two-wavelength digital holograms, the method becomes real-time, in the sense that the surface shape can be measured at each time instant at which the holograms are recorded. Thus, phase shifting and sequential recording are suppressed. However, due to the roughness of the inspected surface, speckle decorrelation occurs and noise is included in the final data. The noise amount in the data must be investigated in order to define the best processing approach for holograms. This paper proposes the analysis of the standard deviation of noise in surface-shape data from two-wavelength spatially-multiplexed digital holograms. The influence of noise on the measurements of the surface shape is described by an analytical approach. Relationships to quantify the minimum measurable surface height is given by taking into account the experimental parameters of the set-up. These parameters are related to the spatial bandwidths, modulation of holograms, saturation ratio, number of electrons in pixels, readout noise, quantization noise, photon noise, and speckle decorrelation due to roughness. The theoretical modeling is discussed and analysis when considering practical situation for industrial surface shape measurements.

Conference Presentation

Citation Download Citation

Matthieu Piniard, Béatrice Sorrente, Gilles Hug, and Pascal Picart "Modelling of the photometric balance for two-wavelength spatially multiplexed digital holography", Proc. SPIE 11783, Modeling Aspects in Optical Metrology VIII, 1178308 (20 June 2021); https://doi.org/10.1117/12.2593719

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