Ilia Roussev

Threshold selection in transform-domain denoising of speckle pattern fringes

A transform-domain fringe pattern denoising technique is presented. The Discrete Cosine Transform (DCT) is applied in a sliding window manner to get an overcomplete image expansion, and then the transform coefficients are thresholded to reduce the noise. We investigate the proper size of the sliding window and the proper threshold level. The latter is determined individually for each window position using a local noise variance estimate. In order to deal with a rather inadequate but simplified noise model, a proportionality factor, related with the speckle size, is found by experiments with digitally simulated speckle fringes. Such a proportionality factor suggests that the technique could be made fully automatic. We demonstrate promising results in denoising of real speckle fringe patterns, obtained through an out-of-plane sensitive Digital Speckle Pattern Interferometry (DSPI) set-up in a process of non-destructive testing of reinforced composite materials deformation.

All-silicon microforce sensor for bio applications

It is well known that for precise biological cell injection the applied forces should be exactly controlled in any specific case. In this paper we present design, prototyping, calibration and testing of a microforce sensor, which fulfils the requirements for injection monitoring of biological cells. It is an axial all-silicon piezoresistive Micro Electro-Mechanical System (MEMS) device. The layout of the all-silicon force sensor is adapted for operation at partial dipping in biochemical solutions. A prototype of this sensor is investigated and its parameters are measured. To verify the applicability of the MEMS for bio-applications, it was used in force monitoring injection of Xenopus Oocyte cells. Force measurements during the injection process and interpretation of the force-penetration curve are presented and discussed. Thus, it has been experimentally proved that the developed all-silicon force sensor can be successfully applied for force monitoring in different bio-applications.

Force sensor for cell injection and characterization

This paper presents the basics idea and principles of a force sensor for cell injection and characterization of mechanical properties of cells. It utilizes fluidics, piezo resistive MEMS, and piezo actuated mechanics to provide sub-micronewton sensitivity in vertical injection mode. The prototyping, calibration and investigation of the proposed sensor are also presented in brief. Main advantages and drawbacks are also discussed.

Roughness Measurement of Dental Materials

Abstract This paper presents a roughness measurement of zirconia ceramics, widely used for dental applications. Surface roughness variations caused by the most commonly used dental instruments for intraoral grinding and polishing are estimated. The applied technique is simple and utilizes the speckle properties of the scattered laser light. It could be easily implemented even in dental clinic environment. The main criteria for roughness estimation is the average speckle size, which varies with the roughness of zirconia. The algorithm used for the speckle size estimation is based on the normalized autocorrelation approach.

Optomechatronic System For Automated Intra Cytoplasmic Sperm Injection

Abstract This paper presents a complex optomechatronic system for In-Vitro Fertilization (IVF), offering almost complete automation of the Intra Cytoplasmic Sperm Injection (ICSI) procedure. The compound parts and sub-systems, as well as some of the computer vision algorithms, are described below. System capabilities for ICSI have been demonstrated on infertile oocyte cells.

DSPI applied to rubber viscoelastic behavior at low stresses study

A thin rubber plate is circumferentially clamped and centrally loaded with a small constant force. The behavior of this elastic membrane is studied through an out-of-plane sensitive Digital speckle-pattern interferometer. The surface deformations of the plate are revealed by a developed program, realizing the phase determining method of Spatial heterodyning. Simulated noisy speckle patterns are used to test the possibilities of the software. The removal of an arising tilt effect, due to a non-whole number of carrier fringes in the analyzed pattern, is shown and discussed. Experimental results are presented for the rubber surface deflection in several consecutive moments during the application of the force, and after its removal. Trajectories of surface points are plotted. A subtle effects of non-linear behavior are visualized.

Two Fringe Evaluation Methods Applied To Thermal Expansion Coefficient Measurements By Speckle-Photography: A Comparison

Two fully automated and essentially different methods for Youngs fringes analysis are applied to thermal expansion coefficient determination of engineering ceramics by double-exposure speckle-photography. The first one creates fringe structures and fits them to the experimental images. The cross-correlation functions between the given image and the generated fringe structure are calculated and serve as a measure of coincidence. In order to reduce the computational demands,the second method analyses the fringe intensity profile along four selected directions.