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Fast quantitative characterization of a rectangular groove with sizes from sub-micrometers to micrometers on a surface has been demanding in quality control of optical elements. We report a numerical procedure for retrieval of the geometrical parameters of a rectangular groove, including width and depth, from the angular distribution of the scattered light generated by launching plane waves on the groove on a metallic surface from different propagation directions. The far-field intensity of scattering light is first obtained by numerically solving the electromagnetic problem with the modal theory. Then, a two-stage inverse modeling approach is developed to retrieve the groove parameters based on the lookup table and repulsive particle swarm optimization from multi-angle scattering light distribution that is highly sensitive to the groove parameters. Noise influences are considered in the simulation. Results suggest that our method can precisely obtain the groove parameters for noisy signals. As the measurement of light scattering can be conducted with high efficiency, it should be a powerful tool to characterize rectangle grooves on metallic surfaces.

This paper presents a design of particle detection system based on optical transmission and scattering method. In this setup, a laser with emitting wavelength of 671 nm is employed. The sample particles are 3.03 um and 7.07 um polystyrene microspheres. Based on Mie scattering theory and Beer-Lambert law, the particle size and particle number concentrations against the scattered light intensity and transmitted light intensity are studied experimentally. The experimental results show that the scattered light intensity increases with the increasing of particle size and particle number concentrations. However, the transmitted light intensity decreases with the increasing of particle number concentrations. In our future work, this system will be applied to platelet aggregation detection. By detecting the transmitted light intensity and scattered light intensity simultaneously, this detection system can achieve more accurate detection.

Single particle identification and characterization based on scatter measurements is widely used in numerous biomedical applications. This scatter-based characterization approach implies a solution of the parametric inverse light-scattering (ILS) problem. The need for high-speed analysis limits the amount of collected scatter information and motivates maximum simplification of optical model of analyzed particles. We analyzed the capabilities and limitations of two existing approaches, based on measurement of either two scattering signals or angle-resolved patterns, applied to characterize single submicron particles. The standard flow cytometric approach is based on light scattering measurements into two fixed angles, forward and side scattering, which are further fitted by the Mie theory. We showed that corresponding ILS problem may have multiple solutions, and the procedure results in uncontrollable errors if the particle is not spherical. By contrast, angle-resolved scattering measurements have much larger information content at a cost of reduced analysis speed. This approach coupled with rigorous solution of ILS problem is shown to provide accurate identification and characterization of biological particles, including nonspherical ones.

We report on conical refraction (CR) experiments with low-coherent light sources such as light-emitting diodes (LEDs) that demonstrated different CR patterns. The change of a pinhole size from 25 to 100 μm reduced the spatial coherence of the LED radiation and resulted in the disappearance of the dark Poggendorf ring in the Lloyd's plane. This is attributed to the interference nature of the Lloyd's distribution and is found to be in excellent agreement with the paraxial dual-cone model of CR.

Turbidity is an obvious and direct indicator of water quality which embodies the existence and concentration of certain particles in water sample to some extent. Quantitative measurement of turbidity by methods with a light intensity sensor at a single angle has been studied adequately whereas the study is rare on methods involving multi-angle light intensity signals. In this paper, an optimization on angle selection of an existing four-angle turbidity measurement method has been discussed. Experiments have been conducted using an 850 nm laser and a power meter. Scattering light intensities at a series of angles are collected to estimate turbidity. Results show that the accuracy can be further improved by using proper angle combinations. Relative estimation error by using optimized angle combination is only about 36% of the existing method in average for the test samples.

This paper describes a semiconductor laser as the light source, Establish a real-time measurements optical system, with an particle number concentration of dust particles in the air. Gives a detailed structural principle of the system and how to use an optical sensor. According to Mie scattering theory, the light scattering characteristics of the response of the optical system. Experimental results show that the system has a high count accuracy, repeatability and counting efficiency for atmospheric PM2.5 monitoring.

In this paper we propose a new light transport refocusing method for depth estimation as well as for investigation inside scattering media with unknown scattering properties. Propagated visible light rays through scattering media are utilized in our proposed refocusing method. We use 2D light source to illuminate the scattering media and 2D image sensor for capturing transported rays. The proposed method that uses 4D light transport can clearly visualize shallow depth, as well as deep depth plane of the medium. We apply our light transport refocusing method for depth estimation using conventional depth-from-focus method and for clear visualization by descattering the light rays passing through the medium. To evaluate the effectiveness we have done experiments using acrylic and milk-water type scattering medium in various optical and geometrical conditions. Finally, we show up the results of depth estimation and clear visualization, as well as with numeric evaluation., 2014 22nd International Conference on Pattern Recognition,Stockholm, Sweden,24-28 Aug. 2014

Using a solution of the radiation transfer equation in the small angle approximation, we examine the effect of multiple scattering on the measurement of the light beam attenuation in an aquatic environment abundant in bubbles created by movement of ship or sea animals. According to the measurement condition, the correction coefficient denoting the extent of multiple scattering is introduced, which is a function of detector field of view (FOV), beam transfer distance, beam size and energy-received section size. Given a typical bubble clouds' distribution function, numerical computations and the analysis between the correction coefficient and its four parameters are provided. The results show that the multiple scattering is obvious when measuring the light attenuation by water filled with large numbers of bubbles, and the degree of multiple scattering changes along with measurement parameters.

For the reconstruction of absorber embedded in a homogeneous scattering medium, a backprojection method using intensity ratio is evaluated numerically. The proposed method uses the intensity ratio between an object medium and a reference medium.

Scattering light from several-ten nanometer defects of an optical diffractive element was investigated with a scatterometer. We firstly demonstrated an agreement between the measurements and computer simulations over 107 dynamic range.

Summary form only given. Time-resolved diffuse optical spectroscopy (TRS) is a valuable technique for the characterization of a variety of diffusive media like biological tissues, fruit, wood and pharmaceutical tablets. The technique is based on the injection of a short pulse (~ps) on the surface of the sample. The time-of-flight distribution (TOF) of photons detected on a different location of the surface gives information about the absorption and scattering probabilities [1]. Due to the widespread application of the technique to biological tissues, where there is a low light attenuation in the 0.6-1.1 μm range, the range beyond 1.1 μm is relatively unexplored with time-resolved techniques, also because of the difficulty to combine mode-locked continuously tunable sources with detectors having a sensitivity down to the single-photon level. Nevertheless beyond 1.1 μm there are organic compounds that contribute to interesting spectral structures like collagen, lipids, hydroxyapatite, starch, glucose and lignin. In this work we explore the application of TRS beyond 1.1 μm to the characterization of a variety of samples.

Summary form only given. There is a strong worldwide drive to efficient general lighting using white light emitting diodes (LEDs) [1,2]. White LEDs often consist of a semiconductor diode [3,4,5] combined with luminescent phosphors [5] to convert part of the blue light to green yellow, and red. In state-of-the art white-light LEDs one exploits multiple scattering of light [1,2]. The transport of light then becomes diffusive, which serves to obtain a desirable smooth lighting without hot spots and without angular color distribution. Moreover, photons are recycled so that thin phosphor layers serve to improve cost efficiency and reduce environmental impact.Central challenges in the understanding of white LEDs arise from limitations in the physical understanding of the combined multiple light scattering and energy conversion in phosphors. LEDs are currently described by raytracing and Monte Carlo techniques [1,2]. Unfortunately, LED spectra cannot be predicted quantitatively, as optical parameters must be adjusted to be inconsistent with other data. These limitations hamper the design and development of efficient white LEDs. An improved description of multiple light scattering could be obtained by analytical theories originating from nanophotonics, invoking detailed nanostructure of a sample. We have measured diffuse optical transmission and reflectivity through diffuser plates typical of a commercial white LED (Fortimo). Using photonic diffusion theory we derive the transport mean free path [6-8]. With increasing scatterer density the mean free path decreases. To interpret the results, we use an ab initio model without free parameters by combining Mie theory with known properties, such as the scatterer size distribution taken from SEM. Our model predicts mean free paths in dramatically improved agreement with our data, without adjustable parameters [9]. We will discuss consequences for light scattering in white lighting modules.

Summary form only given. Random scattering of light that one can observe in paper, paint and biological tissue is an obstacle to imaging and focusing of light and thus hampers many applications. At the same time scattering is a phenomenon of basic physical interest as it allows the study of interference effects such as Anderson localization [1-3], open transport channels [2,4], and speckle correlations [5].Recently the realization has dawned that propagation of laser light in scattering media can be controlled by shaping the incident wavefront [6]. This control relies on the fact that scattering by stationary randomness performs a random linear transformation on the incident light modes. Wavefront shaping methods effectively invert this transform and have given rise to a surge of fundamental studies of light propagation, new modalities of imaging, and focusing of scattered light [6-12]. The resolution of this focusing can exceed that of conventional focusing optics [13,14]. Many of these methods rely on the measurement of a transmission matrix to characterize the scattering medium [15,16], using a probe or detector at the position of the intended focus. Very recently we demonstrated that speckle correlations enable non-invasive fluorescence imaging through strongly scattering layers, without the need of prior calibration [17]. This high-resolution imaging method uses only randomly scattered light. I will discuss the recent rapid advances in methods that exploit scattered light for high-resolution imaging.

Particle Image Velocimetry (PIV) technique produces the velocity vector fields of various aerodynamic flows by the correlation between a set of successive images. The flow is usually seeded by lightweight microscopic particles, which scatter the optical energy towards camera sensors. A monochromatic light sheet illuminates the seeding particles. In large-scale PIV tests, cameras are usually located at a considerable distance from the laser sheet, and sometimes at angles where the light scattering is minimal. This can create dark images, or unbalanced brightness between the different angles of observation, which negatively affect the quality of the image-correlation and velocity measurements. For this reason, we usually choose particles that have a relatively high refractive index for seeding. Fluid droplets with as small diameters as 0.3 microns have recently become popular due to their appealing aerodynamic properties. The scattering pattern can be surprisingly different from one seeding material to another, even when the particles have the same size. The oil droplets have a considerably lower refractive index than the conventional solid seeding particles, and therefore, a lower scattering efficiency. This paper discusses the influence of the refractive index of the seeding particles on the light scattering efficiency using the Mie theory (of scattering) and experimental observations.

The experimental measurement and image processing methods are combined to study the light scattering characteristic from the target, principle of the scaling ratio between the light scattering characteristic and the geometric dimension of the target is presented in this paper. The solar simulator is utilized as a light source which incidence the target with rough surface. The original experimental images must be measured by light receiver and data gathering system. Some image algorithms are be designed to process these experimental data. As a researching example, the imaging light scattering characteristic of two kinds of bigger and smaller simple targets include clubs, cylinders are discussed in detail. The image processed results are shown the scale ratio of the light scattering from target is proportional to its dimensional square. The important of our works is that the scaling rations of the light scattering characteristic can be used to make known the illumination of the whole dimensional detected target, which are useful for further study the complex target such as civilian industries, national defence, air and aero fields.

High intensity sub-wavelength spots and low divergence nanojets are observed in a system of Si 3 N 4 microdisks illuminated from the side with laser light of wavelengths 532 nm and 633 nm. The disks are of height 400 nm with diameters ranging from 1μm to 10 μm. Light scattered from the disk and substrate is observed by imaging from above. In free space light is focused inside the disks and a sub wavelength spot is observed, whereas in water the refractive index contrast is such that photonic nanojets are formed. The angular distribution of the intensity compares well to the analytical solution for the case of an infinite cylinder. The diameter dependence of the scattering is explored and matches well with theory.

The concept of optical path length enhancement is a useful tool for characterizing the effects of light trapping in thin films by providing a convenient geometrical interpetation of energy absorption. However, path length calculations cannot distinguish between absorption gains due to better antireflection versus absorption gains due to actual scattering of incident rays. We therefore introduce a similar metric of equivalent deflection angle to describe the effective scattering of light by a textured surface. This new concept provides useful information about light trapping that path length alone cannot. The paper begins with the geometrical interpretation of the metric and then demonstrates the insights derived from light scattering by a simple textured surface.

We present a new method for the determination of the scattering length of optical photons in scintillator crystals. The new method, based on the direct measurement of the scattered light is compared with the usually applied indirect method. Investigating different samples from two manufacturers, scattering length of 0.55…6.8 m at 405 nm wavelength, and more than 80 m at 532 nm wavelength was determined. Dependence of the scattering length on the polarization of the light, as well as on the crystal sample and its orientation is also discussed.

The effect of absorption inhomogeneity on μ s estimation of a scattering medium with a newly proposed technique was investigated. The estimation error was significantly reduced from that with a conventional technique.

Elastic optical scattering in biological tissue typically dominates over absorption by an order of magnitude or more. Being the dominant light interaction process, scattering prevents tissue from being transparent. Although the spectral properties [1] and angular profiles [2] of scattered light can reveal useful physiological information about a given tissue sample, scattered light is generally regarded as poor in imaging information. This is due to the severe deterioration of the incident light field, caused by disordered amplitude and phase modulation of its wavefront as it propagates through the tissue. Yet, it is also known that elastic optical scattering is a deterministic and time reversible process. In other words, if we can record the phase and amplitude of the propagating scattered light field completely and reproduce a back propagating optical phase conjugate (OPC) field or a time‐ reversed light field this field should be able to retrace its trajectory through the scattering medium and return the original input light field.

Light scattering technique is used to measuring the blood cell size in many types of Hematology Analyzers, but How to choose the detection angle of scattered light affect the efficiency of the instrument count. IN this paper, axial lighting model is established. Mathematical description of luminous flux and particle size of cell is given. And through numerical calculation, the main factors counting efficiency are analysis.

It is valuable to detect concentration of a small quantity of liquid with suspended particles, especially for MEMS. In this paper, a structure is designed with two beams of optical fibers. Light scattering in different direction is simulated and analyzed based on Mie theory in order to find the optimal type of detection. The size character and refractive index have an affect on the extinction coefficient, and more detail simulations are presented in this paper. For different refractive indexes of suspending liquid, real number or complex number, the condition of scattering and absorption to light is analyzed. Based on the study of scattering theory, the comparison structure for concentration detection is presented, which receives light in range from 0 to 180 degree, and variable optical length from 2 to 5mm, the value of angle and length change is straightly shown, respectively. The structure is characteristic of two sessions: rotational part and moving part, which receive the scattering light in any given angle and optical length. In the system design optical fiber is used, which emit light beam to a small sample accurately and receive scattering light. Concentration will be gained according to the detection of emitting and receiving light intensity.

Transmitted light through a diffuse scattering medium includes strongly diffused light (SDL) and weakly scattered light (WSL). To realize clear transillumination imaging through thick body tissue, which is typically more than 10 mm, we developed a technique to extract the WSL component from diffused light. A diffuser is placed on the incident surface of a scattering medium. We can extract the WSL component by subtracting the light intensity at the output surface with a diffuser from that without a diffuser. In CW measurements using a 15-mm-thick scattering medium (reduced scattering coefficient mu s '=1.0/mm), the spatial intensity distribution of the scattered light at the output surface was confined to an approximately 50% area by the proposed technique. It was confirmed in a time-resolved measurement that the earlier time component with a smaller temporal spread was extracted by the proposed technique.

Optical imaging provides richer information than any other imaging technique based on topographic information. However, the spatial resolution in optical microscopy is restricted by the diffraction limits of the probing light, which is a few hundred nanometers for visible light. This problem can be overcome by combining the plasmonic effects of near-field techniques with optical Raman microscopy. In our previous work [1,2], we have shown that Raman scattering combined with near-field microscopy, i.e., tip-enhanced Raman spectroscopy (TERS), provides super spatial resolution far beyond the diffraction limits of the probing light, along with an enhanced scattering efficiency. This is due to the nano-sized evanescent field created in close proximity of the apex of a nano-metallic tip, which enhances the scattering from the sample molecules directly under the tip apex. The image quality, such as the contrast and the resolution, can be further improved by invoking higher-order scattering effects in Raman scattering process because it provides better confinement of light field than the linear scattering due to the nonlinear effects, and better contrast due to the suppression of the luminescence background. We have shown this by utilizing the near-field effects in coherent anti-Stoke Raman scattering (CARS), and have obtained high quality image with a spatial resolution of 15 nm [3].

A novel cryptographic technique based on forward scattering of light by an air structured fibre is proposed and demonstrated. The interference fringe pattern dependence on the fibre angular orientation and incident beam properties is also exploited.

A study of polarized light transmitted through turbid media is described. Spatial distribution of the intensity and the degree of polarization of the transmitted light are measured experimentally and simulated numerically using Monte Carlo method. A CCD (Charge Coupled Device) camera was used in the experiment to capture the profile of the laser source and transmitted light. The experimental and simulation results show that the spatial factors of the scattered light can be used to demarcate tissue optical parameters such as scattering coefficient and absorption coefficient.

We proposed a noninvasive glucose monitor by detection of photons preserving initial polarization using phase-modulator. The slight change of scattering coefficient by addition of glucose was detected as a phase-modulated light in highly scattering medium.

Light depolarization by Mie scatterers of arbitrary size and refractive index is studied analytically. The isotropization length l/sub p/ responsible for light linear depolarization is presented. Linear and circular depolarization by Mie scatterers is addressed quantitatively.

The shape of particles and their orientations in space are of importance in the manufacture of aerosols, paints and coatings, pharmaceuticals and to sensing and imaging through turbid random media The use of polarised radiation affords a greater flexibility to address these characteristics through the use of light scattering techniques In the case of scattering by many very small particles, polarisation ratios, distributions and correlation functions of scattered polarised light all require additional information to resolve measurement ambiguities. However, we have recently shown [1] that the shape of the probability density of scattered radiation from a single small scatterer provides a means to determine the shape of spheroidal particles uniquely.

A success of practical implementation of the well known method of thermal dynamic grating (TDG)1-3 in the contactless measurements of thermal diffusivity x of solids essentially depends on acceptable thermal excitation of the sample in order to obtain a quite noticeable signal of diffraction and on suppression of forward probe beam scattering caused by sample imperfections. In addition a theoretical model should be simple enough with the number of controlled parameters as low as possible.

Images are presented which were constructed using visible light transmitted through a simple breast phantom. They reveal the presence of small opaque features distributed within the phantom, despite the fact that all the detected photons had been scattered many hundreds of times. The images were generated by recording the intensity of the transmitted light as a function of time, and measuring the very small amount which is scattered along a path close to the straight line between the source and the detector.

We consider the light collection in scintillators as a process of light propagation in the dynamic system with elastic (mirror) reflections. It has been shown that the light yield is strongly dependent upon the type of regular and/or chaotic dynamics of light rays. The chaotic light yield is described by a new formula generalizing the "formula of photometry sphere". Using theoretical expressions, some geometric-optical factors affecting the light collection were analyzed. Increase in the light output (by tens of per cent) is possible in systems with asymmetric (non-Lambert) indicatrix or in systems with essential light scattering, e.g., in the presence of internal scatters.

There are shortcomings for light interferometry-based non-contact microscopic surface measurements when used in-process, thus this study proposes an enhanced measurement method based on light reflectivity. Although reflected light contains information about surface shape, the entire surface profile cannot be measured directly such as in the interferometry-based method. Therefore, a different approach is used to overcome these limitations: a detailed surface model is developed from surface height and spatial frequency. Light reflectance theory is adopted to simulate light scattering in many virtual specimens, which are generated by a light reflectance model. As a result, a notable correlation between surface components and reflected light has been established. Even though either simulations or experiments can reveal the correlation as a numerical formula, one of the surface components is used separately, thus a signal-processing algorithm to decompose surface components is proposed in this study. In order to prove the reliability of the newly proposed measurement scheme, experiments are conducted using a fabricated optical probe.

We propose a Monte Carlo method which can simulate scattering of polarized light in sphere suspension and also present a basic system for 2-D angular pattern of the backscattering light from turbid media. The experimental results of polystyrene sphere suspension coincide well with the simulation results.

Time-resolved backscattering profiles of circularly and linearly polarized light were measured. The experimentally observed polarization memory effect is used to enhance the image contrast for a target inside large particle suspensions.