Mr. Paul Retief Profile

Paul Retief

Principal scientist at Incomar Aerospace and Defence Systems

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Author

Area of Expertise:

infrared , data reduction , measurements , mathematical modelling

Websites:

Company Website | Personal Website

Publications (3)

Proceedings Article | 23 June 2014 Paper

Infrared recordings for characterizing an aircraft plume

S. J. Retief, M. Dreyer, C. Brink

Proceedings Volume 9257, 92570C (2014) https://doi.org/10.1117/12.2066290

KEYWORDS: Atmospheric modeling, Black bodies, Carbon dioxide, Mid-IR, Infrared radiation, Electro optical modeling, Mathematical modeling, Infrared cameras, Cameras, Molecules

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Proceedings Article | 8 November 2012 Paper

Aircraft plume infrared radiance inversion and subsequent simulation model

S. J. Retief

Proceedings Volume 8543, 85430P (2012) https://doi.org/10.1117/12.970539

KEYWORDS: Absorption, Transmittance, Infrared radiation, Mid-IR, 3D modeling, Infrared imaging, Thermal modeling, Imaging systems, Missiles, Image segmentation

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A radiance inversion technique, in which in-flight aircraft plume radiance recordings are exploited to construct a three dimensional (3D) radiance model of the plume, is presented. The recordings were done with a mid-wave infrared (3 – 6 μm) camera at different altitudes. The algebraic formulation of this inversion technique, also known as an emission-absorption technique, is stated for the ideal case of spectral radiance measurements of a high spatial sampling resolution over the plume area, as would be obtained from a hyperspectral imager. The non-ideal case of having only broad-band (mid-wave) image measurements and only one spectral measurement of the plume, is then investigated. It is shown that from this incomplete information set, an effective spectral absorption coefficient can be calculated for which the associated plume spectral transmittance and spectral emissivity calculations exhibit the correct qualitative behaviour. It is also shown that, by using this effective absorption coefficient, an optimization procedure can be used to determine the temperatures and/or spectral radiance values within the plume. This optimization procedure consists of minimizing the difference between the observed line of- sight (LOS) radiance in the image (i.e. a pixel radiance value in the image) and its theoretical projected radiance. After the temperature values within the plume were determined, the observer LOS radiance is parameterized so that it can be described for an arbitrary angle with respect to the main axis of the plume. The inferred temperature, spectral transmittance and spectral emissivity are then used in calculating the expected spectral radiance at this arbitrary angle. The spectrally integrated/mid-wave broad-band radiances and intensities for aspect angles other than those used during the inversion process, are then calculated and compared with actual measurements in order to determine the adequacy of this model for incorporation into existing infrared imaging system simulation software used in the training of infrared seekerhead missiles.

Proceedings Article | 14 August 2003 Paper

Prediction of thermal crossover based on imaging measurements over the diurnal cycle

S. J. Paul Retief, C. J. Willers, M. S. Wheeler

Proceedings Volume 5097, (2003) https://doi.org/10.1117/12.488358

KEYWORDS: Temperature metrology, Thermography, Climatology, Thermal modeling, Monte Carlo methods, Data modeling, Infrared imaging, Infrared radiation, Image acquisition, Sun

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