Dynamic properties of speckled speckles

Hanson, Steen Grüner; Iversen, Theis Faber Quist; Hansen, René Skov

doi:10.1117/12.870934

Cited by 5 publications

(5 citation statements)

References 14 publications

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“…By placing the samples in the water, the light-MP interaction further modifies the initially generated speckle pattern. Considering the originally generated speckle pattern from the rough glass disk, we can consider the speckle pattern recorded in the detection plane of the CCD camera as a form of speckled speckle [19]. Although the pristine, flat, curved, or rough MPs differently modifies the initially generated speckle pattern by the rough glass disk, we simply refer to the obtained images on CCD as a speckle pattern.…”

Section: Methodsmentioning

confidence: 99%

Laser beam scattering for the detection of flat, curved, smooth, and rough microplastics in water

Asamoah

Amoani

Roussey

et al. 2020

Opt Rev

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Microplastic (MP) pollution is alarming and poses an imminent threat to the environment with a direct impact on our health and that of fauna in natural water bodies. The understanding of light-MP interactions in water as well as the need for low-cost and robust optical sensors for the detection of MPs that appear everywhere is, therefore, necessary. We have demonstrated the use of a prototype optical sensor in the detection of flat and curved [from polyethylene terephthalate (PET) water bottle] pristine and rough MPs from commercial PET and low-density polyethylene plastics in water. The optical sensor utilizes a photodiode and charge-coupled device (CCD) camera to record simultaneously the specular reflection and the speckle pattern modified by the MPs. In this study, we have exploited the specular reflection in the detection of the pristine samples, whereas the speckle contrast, the normalized standard deviation of the speckle pattern intensity, is utilized in the qualitative estimation of the "effective" surface roughness of the MPs. With the sensor, one can, therefore, detect PET MPs with varying average surface roughness, Ra an indication of MP aging, embedded in water. The prototype can detect the effect of size, type, curvature, transparency, and the translucency of sunken and/or floating MPs in water based on the reflection, scattering, and the (edge) diffraction of light. However, the optical sensor is limited in the discrimination of MP concentration in water. Further modifications to the sensor are needed for its practical implementation in complex natural water bodies and wastewaters.

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Section: Methodsmentioning

confidence: 99%

Laser beam scattering for the detection of flat, curved, smooth, and rough microplastics in water

Asamoah

Amoani

Roussey

et al. 2020

Opt Rev

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“…hIr; t 1 i 1 can be obtained from Eq. (2), which means that the average intensity of the field Er; t is constant over all space. This arises due to the use of a delta-correlation model for D 1 .…”

Section: Theoretical Analysismentioning

confidence: 99%

“…This kind of speckle field generation is described as involving a random process being driven by another random process. Doubly scattered speckle is sometimes referred to as speckled speckle [1,2].…”

Section: Introductionmentioning

confidence: 99%

K speckle: space–time correlation function of doubly scattered light in an imaging system

Kelly

Sheridan

2013

J. Opt. Soc. Am. A

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The scattering of coherent monochromatic light at an optically rough surface, such as a diffuser, produces a speckle field, which is usually described by reference to its statistical properties. For example, the real and imaginary parts of a fully developed speckle field can be modeled as a random circular Gaussian process. When such a speckle field is used to illuminate a second diffuser, the statistics of the resulting doubly scattered field are in general no longer Gaussian, but rather follow a K distribution. In this paper we determine the space-time correlation function of such a doubly scattered speckle field that has been imaged by a single lens system. A space-time correlation function is derived that contains four separate terms; similar to the Gaussian case it contains an average DC term and a fluctuating AC term. However, in addition there are two terms that are related to contributions from each of the diffusers independently. We examine how our space-time correlation function varies as the diffusers are rotated at different speeds and as the point spread function of the imaging system is changed. A series of numerical simulations are used to confirm different aspects of the theoretical analysis. We then finish with a discussion of our results and some potential applications, including controlling spatial coherence and speckle reduction.

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“…where G 1 (u, v; ξ, η) is the Green's function connecting propagation between the first and second diffuser through an imaging lens. 17 Thus the properties of the imaging system will be completely described if the Green's Function G 1 (u, v; ξ, η) can be specified. If the optical system is to produce high-quality images, then U s must be as similar as possible to U o .…”

Section: Theoretical Descriptionmentioning

confidence: 99%

“…As per the generalised ray-matrix formulation, when B 1 equals zero, the image of the first diffuser coincides with the second diffuser, and the gearing becomes zero. 17 Accordingly, this corresponds to a z-value of 2.2 mm. The decorrelation of the speckles revealed through decreasing intensity of peaks though remains similar, the correlation width varies as a function of z.…”

Section: Experimental Analysismentioning

confidence: 99%

Investigation of transverse motion of concealed scatterer using correlation of speckled speckles from static surface layer

Nair

Vinu

Naik

et al. 2018

Reflection, Scattering, and Diffraction From Surfaces VI

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Speckle-based techniques have noteworthy applications in the field of material science, surface characterization, determining mechanical displacements, biological activity in diffuse layer, imaging through turbid layer etc. The passage of coherent light through a diffuse layer generates a random speckle pattern, which have the inherent feature of carrying information associated with the diffuse layer. Dynamic laser speckle associated with the displacements of scattering surface has prominent impacts in the study of biological activity inside the diffuse layer. Investigations are progressing in the direction of exploring the dynamical properties associated with speckled speckles and its applications in imaging and characterization scenarios. In this work, we theoretically and experimentally study the dynamical properties of speckles through a static scattering layer using intensity correlation. The displacement (transverse or angular) produced in the concealed scatterer generates the dynamic speckle pattern which is observed through a second static diffuser. We expect to find applications of this investigation into the tracking objects hidden in the diffuse layer, measuring biological activity in diffuse layer, displacement measurements, etc.

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Dynamic properties of speckled speckles

Cited by 5 publications

References 14 publications

Laser beam scattering for the detection of flat, curved, smooth, and rough microplastics in water

Laser beam scattering for the detection of flat, curved, smooth, and rough microplastics in water

K speckle: space–time correlation function of doubly scattered light in an imaging system

Investigation of transverse motion of concealed scatterer using correlation of speckled speckles from static surface layer

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