On-line particle size and velocity measurements by the analysis of defocused images: extended depth of field

Denis Lebrun; Cafer Ozkul; C. E. Touil; J. B. Blaisot; Alain Kleitz

doi:10.1117/12.168074

1 February 1993 On-line particle size and velocity measurements by the analysis of defocused images: extended depth of field

Denis Lebrun, Cafer Ozkul, C. E. Touil, J. B. Blaisot, Alain Kleitz

Author Affiliations +

Proceedings Volume 2088, Laser Dimensional Metrology: Recent Advances for Industrial Application; (1993) https://doi.org/10.1117/12.168074
Event: Laser Dimensional Metrology: Recent Advances for Industrial Application, 1993, Brighton, United Kingdom

Abstract

We are dealing with the description of an optoelectronic instrument which does not necessarily need in-focus images for dimensional measurements. Assuming the point spread function (PSF) as Gaussian, spherical particle diameters are deduced from the image contrast and the cross-section areas of the defocused images. Here, a cross-section area is defined by the number of pixels whose grey level is inferior to the mid-point intensity. The instrument makes use of two CCD cameras with the same angle of view. The source is a double pulsed multimode laser diode. One of the CCD cameras is exposed to two pulses and the activation of the other is delayed for only recording the object field illuminated by the last pulse. Then the two video signals are subtracted. This operation increases the signal/noise ratio (SNR). The contrast of one image being inversed, not only the amplitude of the particle velocity but also its sign, can be determined.

Citation Download Citation

Denis Lebrun, Cafer Ozkul, C. E. Touil, J. B. Blaisot, and Alain Kleitz "On-line particle size and velocity measurements by the analysis of defocused images: extended depth of field", Proc. SPIE 2088, Laser Dimensional Metrology: Recent Advances for Industrial Application, (1 February 1993); https://doi.org/10.1117/12.168074

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