다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

We review the recent developments in the area of optical fiber grating sensors, including quasi-distributed strain sensing using Bragg gratings, systems based on chirped gratings, intragrating sensing concepts, long period-based grating sensors, fiber grating laser-based systems, and interferometric sensor systems based on grating reflectors.

Fiber grating sensors

The PASCAL Visual Object Classes Challenge

A simple lateral shearing interferometer is proposed for measuring refractive index of thin parallel plate silicon sample. The rotating sample works as lateral shearing element. As the sample rotates a continuous lateral shearing is obtained owing to the change of the optical path difference (OPD) between the transmitted beam and that first reflected by the surface sample. The recorded interferometric signal is Fourier-transform analyzed and the phase change is determined as a function of the rotating angle. If the thickness of the silicon sample is known the method provides accurate measurement of the refractive index. ( Summary only available )

Lateral shearing interferometer for measuring refractive index of silicon

Microelectromechanical systems (MEMS) are microdevices composed of mechanical elements, electronics, sensors, and actuators, built within a small volume.1 They have several everyday uses, such as within mobile phones, cars, game consoles, and printers. MEMS devices are fabricated by superimposing various layers of different materials, through a number of process steps, on top of a silicon substrate.1 These complex procedures, however, can cause damage or introduce residual stresses to the structures. As a result, unwanted deformations can compromise the final performance of MEMS devices. In addition, the performance of MEMS devices can deteriorate because of aging. The characterization of mechanical properties at different manufacturing steps, or during the mode of operation, is therefore required to provide a full characterization of these systems. In standard characterizations of MEMS, conventional optical microscopy techniques are generally used. With these techniques, however, it is not possible to obtain a full 3D profile of the structures. This is because of an intrinsic limitation to the spatial resolution of the measurements along the z-axis.2, 3 In addition, it has previously been demonstrated that digital holography (DH) can be used to investigate engineered surfaces on the microscale level and thus overcome some of the limitations of classical microscopy.4 In this work,5 we describe and illustrate the general principles of DH for microscale characterizations. The DH process is based on recording of the interference pattern that exists between object and reference coherence waves, with the use of a digital device (e.g., a CCD or CMOS).4 DH has been made possible because of the technological evolution of camera sensors and computers, i.e., because it is now possible to implement hologFigure 1. Illustration of the double exposure digital holography technique and lateral shearing interferometry (LSI) approach for investigating the metrology of a microelectromechanical systems (MEMS) device. (a) A scanning electron microscope image of the device. (b) Wrapped phase map of the MEMS, obtained from the original double exposure hologram. (c) A ‘shearogram’ of the device, in which the curvature of the object is superimposed on a linear term (the result of the LSI subtraction). (d) The MEMS shearing, without the linear term. (e) Profile of the MEMS phase along a central row of the phase map. (f) The resultant phase map of the MEMS. rad: Radians.

Characterizing microelectromechanical systems with digital holography

Composites represent the evolution of the material science and technologies. They are obtained by combining two or more materials of different nature with the aim of exploiting any synergies between the characteristic performances of the raw materials. Their properties, in fact, are influenced by those of the starting components but also by the quality of the interface generated between the combined phases as well as by their mutual distribution. The interphase, even if of minimal extension with respect to the main phases constituting the composite, plays a significant role in the control of the damage mechanisms, determines the breaking strength and the stress / deformation behavior of composite materials. In this work we study the effect of low pressure plasma treatment on intrinsically hydrophilic flax fiber fabrics to improve their adhesion to a hydrophobic polypropylene matrix. The fibers are treated using nitrogen (N2) plasma with four different exposure times. The interfacial adhesion actually achieved was indirectly quantified by interlaminar shear strength measurements. After this, the damaged areas were measured with non-destructive techniques, i.e. Electron Speckle Pattern Interferometry and Lock-in thermography.

Investigation of the influence of plasma treatment of flax fiber fabrics on the mechanical properties of polypropylene-based composites

Quantitative imaging and three dimensional (3D) morphometric analysis of flowing and not-adherent cells is an important aspect for diagnostic purposes at Lab on Chip scale. Diagnostics tools need to be quantitative, label-free and, as much as possible, accurate. In recent years digital holography (DH) has been improved to be considered as suitable diagnostic method in several research field. In this paper we demonstrate that DH can be used for retrieving 3D morphometric data for sorting and diagnosis aims. Several techniques exist for 3D morphological study as optical coherent tomography and confocal microscopy, but they are not the best choice in case of dynamic events as flowing samples. Recently, a DH approach, based on shape from silhouette algorithm (SFS), has been developed for 3D shape display and calculation of cells biovolume. Such approach, adopted in combination with holographic optical tweezers (HOT) was successfully applied to cells with convex shape. Unfortunately, it’s limited to cells with convex surface as sperm cells or diatoms. Here, we demonstrate an improvement of such procedure. By decoupling thickness information from refractive index ones and combining this with SFS analysis, 3D shape of concave cells is obtained. Specifically, the topography contour map is computed and used to adjust the 3D shape retrieved by the SFS algorithm. We prove the new procedure for healthy red blood cells having a concave surface in their central region. Experimental results are compared with theoretical model.

Lab on chip optical imaging of biological sample by quantitative phase microscopy

We describe a long-wavelength Mach-Zehnder interferometer for digital off-axis Fresnel holography with a pyro-electric detector array used to record digital holograms of an extended object at 10.6 μm. We show that, although the spatial resolution of the pyro-electric detector array is much less than that of typical CCD cameras working in the visible region, good reconstruction of the amplitude and phase of the object wavefield can be obtained. The principle of Fresnel reconstruction in digital holography is described and results of reconstruction process for object size of the order of 700 μm are presented and discussed.

Pietro Ferraro

Papers

Lateral shearing interferometer for measuring refractive index of silicon

Characterizing microelectromechanical systems with digital holography

Investigation of the influence of plasma treatment of flax fiber fabrics on the mechanical properties of polypropylene-based composites

Lab on chip optical imaging of biological sample by quantitative phase microscopy

Infrared digital holography