Digital in-line holography for the characterization of flowing particles in astigmatic optical systems

Contribution of Debye series to particle characterization with holography and the photonic jet method

“…As already mentioned, except the term p=0 diff , all other optical phenomena are commonly neglected in DIH literature -without any justification. By now, we have already proven indirectly that it is mandatory to account for the term p=1 (single refraction) to reproduce the main features of the PJ [2][3][4]. The results obtained with the Debye theory show that this term is not sufficient to reproduce all the fine structure of the PJ, see Fig.…”

“…the Tenengrad variance of the modulus of the reconstructed field and the variance of its imaginary part respectively. The reader is referred to [2][3][4] for more details on the mathematical, the numerical, the backpropagation and tracking schemes as well as experimental tests, in free [3,4,14] or astigmatic media [2]. Note that the MATLAB TM code allowing the calculation of the near field and hologram with Debye series is available upon request from the authors.…”

“…We have recently proposed a new and numerical-effective method to measure with Digital-in-Line Holography (DIH)[1] the refractive index (real, m) of transparent and spherical particles [2][3][4]. This "photonic jet method" (PJM) is based on the analysis of the "photonic jet" (also named "forward caustic" [3,5]) produced by the aforementioned particles.…”

Recent developments in high speed imaging and applications in speckle light

“…Exposure time is 1µs to freeze the secondary droplets. The distance between the lens less camera and the droplets must be large enough to avoid damage by the shockwave and short enough to ensure a good sampling of the hologram 27,28 . Considering the pixel size and pitch, the minimal distance is about 33.6cm between the sensors and the droplets.…”

Photonic jet reconstruction for particle refractive index measurement by digital in-line holography

“…In this paper, we propose a new and computationally efficient approach for determining the refractive index of spherical refracting particles using DH. The method is derived from the analysis [13] of the photonic jet generated by refracting particles when they are illuminated by a coherent light beam [14]. During the last decade, this optical near-field caustic [15] was extensively studied numerically [14,[16][17][18] and experimentally [16,19].…”