Full-field particle velocimetry with a photorefractive optical novelty filter

Woerdemann, Mike; Holtmann, Frank; Denz, Cornélia

doi:10.1063/1.2955842

Cited by 12 publications

(3 citation statements)

References 16 publications

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“…After a change in the image information has been detected, the system adapts to this new condition and the output in the signal channel decays exponentially [18]. The time necessary for this adaptation is determined by the characteristic time constant of the photorefractive material and can be tuned by the total light intensity on the crystal from seconds to hundreds of milliseconds for barium titanate [20,21].…”

Section: Dynamic Phase-contrast Microscopymentioning

confidence: 99%

Depth-resolved velocimetry of Hagen–Poiseuille and electro-osmotic flow using dynamic phase-contrast microscopy

et al. 2010

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We quantitatively investigate the axial imaging properties of dynamic phase-contrast microscopy, with a special focus on typical combinations of tracer particles and magnifications that are used for velocimetry analysis. We show, for the first time, that a dynamic phase-contrast microscope, which is the integration of an all-optical novelty filter in a commercially available inverted microscope, can visualize threedimensional velocity fields with a significantly reduced optical sectioning depth. The depth of field for dynamic phase-contrast microscopy is extracted from the three-dimensional response function and compared with the respective values for incoherent bright-field illumination. These results are then used to perform a depth-resolved particle image velocimetry analysis of Hagen-Poiseuille as well as electro-osmotically actuated flows in a microchannel.

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Section: Dynamic Phase-contrast Microscopymentioning

confidence: 99%

Depth-resolved velocimetry of Hagen–Poiseuille and electro-osmotic flow using dynamic phase-contrast microscopy

et al. 2010

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“…Therefore this system is often described as a temporal high pass filter, which detects temporally dynamic signals while suppressing the static background (novelty filter) [23]. This behaviour leads to several applications of the method, ranging from bio-compatible dynamic phase contrast microscopy [24] to micro-flow velocity field analysis [25]. Moreover, the output intensity I out is directly dependent on phase variations introduced to the signal beam.…”

Section: Dynamic Phase Contrastmentioning

confidence: 99%

Label-free analysis of microfluidic mixing processes by dynamic phase contrast microscopy

Holtmann¹,

Eversloh²,

Denz³

2009

J. Opt. A: Pure Appl. Opt.

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We demonstrate a dynamic phase contrast microscope based on photorefractive holographic interferometry. This system allows us to quantify concentration changes during micro-mixing processes by measuring the change of the optical path length. Therefore, no labelling processes with dyes or tracers are needed. The obtained interferograms are evaluated by an intensity analysis of every pixel, resulting in a high lateral resolution of about one micrometre, and the possibility of real-time phase determination. Due to the interferometric nature of the method the phase measurement is unambiguous for optical phase changes in the interval of zero to π radians. We present the expansion of the phase measurement range by a two-wavelength method, allowing us to resolve concentration changes down to 4 × 10 −6 mol cm −3 and quantify concentrations up to 10 −3 mol cm −3. The result is an optimization of the resolution by a factor of two and of the dynamic range by a factor of six in comparison to the single-wavelength technique.

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“…This arises from parasitic gratings created from the interference of the laser beam with its own scattered light, which is intensified through photorefractive two-wave mixing at the expense of the original beam. The resulting destruction of the beam shape hinders photonic applications like holographic spectral filtering [3][4][5][6], optical image processing [7,8], and holographic diffractive beam shaping [9]. However, light-induced scattering can also be useful for material characterization [10,11].…”

Section: Introductionmentioning

confidence: 99%

Light-induced scattering of femtosecond laser pulses in iron-doped lithium niobate crystals

et al. 2009

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Self-amplification of weak scattered coherent light waves in photorefractive crystals leads to losses, known as light-induced scattering or holographic scattering. We find with 532 nm light that it is reduced in LiNbO 3 :Fe for femtosecond laser pulses as compared to cw laser light. Light-induced scattering of pulses is completely absent in samples with sufficiently small Fe 2+ content, in contrast to the scattering of cw light. Additional differences include a slower buildup time, a weaker Bragg selectivity, and a narrower angular distribution of the scattered light for pulsed illumination. The differences can be attributed mainly to the smaller temporal coherence of pulses.

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Full-field particle velocimetry with a photorefractive optical novelty filter

Cited by 12 publications

References 16 publications

Depth-resolved velocimetry of Hagen–Poiseuille and electro-osmotic flow using dynamic phase-contrast microscopy

Depth-resolved velocimetry of Hagen–Poiseuille and electro-osmotic flow using dynamic phase-contrast microscopy

Label-free analysis of microfluidic mixing processes by dynamic phase contrast microscopy

Light-induced scattering of femtosecond laser pulses in iron-doped lithium niobate crystals

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