Wavefront sensing for single view three-component three-dimensional flow velocimetry

3D particle positioning by using the Fraunhofer criterion

“…There are other approximations where the particle position is determined by using complicated experimental arrangements, and the numerical model to calculate the particle position neglects physical parameters of the particle such as light illumination, particle and medium refractive index [15][16][17][18][19][20][21][22][23][24][25][26][27]. Other authors, for its simplicity have used in-line digital holography to determine particle position [3,[7][8][9][10].…”

“…Nowadays optical techniques for 3D particle positioning include scanning techniques [1], stereoscopic imaging [2], holographic methods [3][4][5][6][7][8][9][10] and quantitative defocusing methods [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. These methods can be applied for the analysis of macro-or micro-fluids applications depending on the experimental arrangement utilized to fulfill such purpose.…”

Three-dimensional particle imaging by defocusing method with an annular aperture

“…However, the small apertures used make these techniques optically inefficient and restrict the applications to those where brighter, typically larger, tracer particles can be used. Wavefront sensing has recently been applied to 3C3D particle velocimetry [2,10] but, despite being optically efficient and compatible with coherent and incoherent sources, can only be used with flows where the seed density is kept relatively low.…”

“…The approach offers a simple optical configuration and by locating the clear annulus toward the outer edge of the imaging lens the optical efficiency is maximized and is Ͼ5ϫ the total aperture area used in DDPIV. With respect to existing wavefront sensing techniques for 3C3D measurement [10] this technique can resolve overlapped particle images, which appear as interlocking rings and thereby offer increased spatial resolution for 3D velocity measurements in fluid flows. Moreover, the technique can also be applied in microscopy.…”

Recent Developments of PIV towards 3D Measurements

“…Two cameras in a stereoscopic setup are used to measure the 3C velocity fields corresponding to the three planes. In a recent study, anamorphic imaging and imaging at several planes through a distorted grating were investigated, yielding depth resolution of less than 10 μm -the best value yet achieved [19].…”