• Title/Summary/Keyword: limited diffraction

Search Result 115, Processing Time 0.019 seconds

Limited View Diffraction Tomography by Inversion of Scattered Data (제한된 View에서의 산란 데이터의 역산에 의한 회절 단층영상법)

  • 최종호;최종수
    • Journal of Biomedical Engineering Research
    • /
    • v.5 no.1
    • /
    • pp.25-32
    • /
    • 1984
  • In this paper a new "limited view frequency correlation algorithm" for diffraction topography is proposed. In this algorithm the problem of limited view sampling is solved by spectrum of spatial frequencies of refractive index. This algorithm is very important in a view of reduction of scanning time and improvement of considerably higher image quality object reconstruction.struction.

  • PDF

Residual Stress Measurement on Welded Specimen by Neutron Diffraction (중성자 회절을 이용한 용접부위의 잔류응력 측정)

  • 박만진;장동영;최희동
    • Journal of Welding and Joining
    • /
    • v.20 no.2
    • /
    • pp.50-58
    • /
    • 2002
  • Residual stress is generated in the structures as a result of irregular elastic-plastic deformation during fabrication processes such as welding, heat treatment, and mechanical processing. There are several factors attributed to the origin of residual stresses, tensile or compressive. The stresses can be determined by destructive ways or nondestructive ways using X-ray or neutron diffraction. Although X-ray diffraction is a well established technique, it is practically limited to near-surface stresses. Neutrons penetrate easily into most materials and neutron diffraction permits non-destructive evaluation of lattice strain within the bulk of large specimens because the radiation is more deeply penetrating for metallic engineering components. This paper presented application of neutron diffraction technique to the residual stress measurement using 20 mm thick welded stainless steel plate($100{\times}100 \textrm{mm}^2$)

Boundary Element Analysis for Diffraction of Water Waves with Vertical Cylinders (연직 해양구조물로 인한 파랑회절의 경계요소 해석)

  • 김성득;이성대;박종배
    • Journal of Korean Society of Coastal and Ocean Engineers
    • /
    • v.1 no.1
    • /
    • pp.63-70
    • /
    • 1989
  • A numerical analysis of the wave characteristics of wave diffraction and the interference effects for a single cylinder and for two cylinders were carried out by the Boundary Element Method using constant elements. The Present investigation was limited to the diffraction of 2-dimensional linear waves by vertical impervious cylinders. Numerical model has been written to calculate the wave diffraction coefficient both on the boundary of the cylinders and at points away from it. The accuracy of the computational scheme was investigated by comparing the analytical results of the other reseraches. Good agreement was observed.

  • PDF

Design of Diffraction Limited Head Mounted Display Optical System Based on High Efficiency Diffractive Elements

  • Tehrani, Masoud Kavosh;Fard, Sayed Sajjad Mousavi
    • Current Optics and Photonics
    • /
    • v.1 no.2
    • /
    • pp.150-156
    • /
    • 2017
  • A diffraction limited optical system for head mounted displays (HMDs) was designed. This optical system consists of four modules, including 1:5 mm and 5:30 mm beam expanders, polarization grating-polarization conversion system (PG-PCS) and refractive/diffractive projection optical module. The PG-PCS module transforms the unpolarized Gaussian beam to a linearly polarized beam and it simultaneously homogenizes the spatial intensity profile. The optical projector module has a $30^{\circ}$ field of view, a 22 mm eye relief, and a 10 mm exit pupil diameter with a compact structure. Common acrylic materials were utilized in the optical design process; therefore, the final optical system was lightweight. The whole optical system is suitable for a 0.7 inch liquid crystal on silicon microdisplay (LCOS) with HDTV resolution ($1920{\times}1080$) and $8.0{\mu}m$ pixel pitch.

Diffraction-Limited Beam for One Dimensional Array in Ultrasonic Imaging (초음파 영상에서 선형어레이를 이용한 제한회절빔의 발생)

  • Jeong, Mok-Geun;Song, Tae-Gyeong;Park, Song-Bae
    • The Journal of the Acoustical Society of Korea
    • /
    • v.14 no.2E
    • /
    • pp.87-90
    • /
    • 1995
  • A new solution to the two-dimensional scalar wave equation is presented, which descries a diffraction-limited beam maintaining the lateral field response expressed by the sinc function. Physically, it is a superposition of plane waves having different wavelengths traveling in different directions. The beam can attain a line focus with one-dimensional array transducer in ultrasonic medial imaging.

  • PDF

Lateral Resolution Enhancement in Confocal Self-interference Microscopy with Commercial Calcite Plate

  • Kang DongKyun;Yoo HongKi;Lee SeungWoo;Gweon Dae-Gab
    • Journal of the Optical Society of Korea
    • /
    • v.9 no.1
    • /
    • pp.32-35
    • /
    • 2005
  • In light microscopy, spatial resolution is limited by diffraction effect. Confocal microscopy has improved resolutions in both lateral and axial directions, but these are still limited by diffraction effect. Confocal self-interference microscopy (CSIM) uses interference between two perpendicularly polarized beams to enhance lateral resolution. In previous research, we proposed a calcite plate with its optic-axis perpendicular to the propagation angle and one of the boundary surfaces of the plate. This type of plate is not widely used to our knowledge. In this paper, we change the calcite plate to more common one, which is commercially available. This calcite plate has its optic axis in the plane of incidence. We analyze the characteristics of this calcite plate and numerically compare the performances of CSIM in previous research and CSIM with the commercial calcite plate. Numerical results show improved performance when using the commercial calcite plate

Preparation and Characterization of Suvarna Bhasma Parada Marit - Characterization of Suvarna Bhasma Parada Marit -

  • Thakur, Kapil;Gudi, Ramacharya;Vahalia, Mahesh;Shitut, Shekhar;Nadkarni, Shailesh
    • Journal of Pharmacopuncture
    • /
    • v.20 no.1
    • /
    • pp.36-44
    • /
    • 2017
  • Objectives: The goal of this study was to characterize Suvarna Bhasma Parada Marit by using the Ayurvedic test parameters, physico-chemical tests, and various instrumentation techniques. Methods: Suvarna Bhasma, an Ayurvedic formulation manufactured as per Bharat Bhaishajya Ratnakar 5/8357 (BBR), has been studied using various instrumentation techniques: X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), laser particle size distribution (PSD) analysis, fourier transform infrared spectroscopy (FT-IR), and atomic absorption spectroscopy (AAS), and physico-chemical parameters, such as the loss on drying (LOD), loss on ignition (LOI), and acid insoluble Ash (AIA) were determined. In addition, Ayurvedic tests, such as Rekhapurnatva (enterable in the furrows of the fingers), Varitaratwa (floatable over water), Nirdhoomta (smokeless), Dantagre Kach-Kach (gritty particle feeling between the teeth), were performed. Results: The XRD study showed Suvarna Bhasma to be crystalline in nature and to contain more than 98% gold. The mean size of the gold crystallites was less than 10 microns, and the morphology was globular and irregular. Suvarna Bhasma contains gold as its single and major element, with EDAX and FT-IR spectra showing that it is more than 98% pure gold. The moisture content (LOD) is less than 0.5%, the LOI is less than 2%, and the AIA is not less than 95%. The Ayurvedic tests, as specified above, helped to confirm the quality of Suvarna bhasma prepared as per the text reference (BBR). Conclusion: This chemical characterization of Suvarna Bhasma performed in this study by using modern instrumentation techniques will be helpful in understanding its pharmacological actions and will help in establishing quality protocols and specifications to substantiate the safety, efficacy & quality of Suvarna Bhasma.

A Study on the Development of Measurement Setup for Crater Wear by Diffraction Grating in Turning (선삭에서 회절격자를 이용한 크레이터마모 측정장치 개발에 관한 연구)

  • Kim, Yeong-Il;Kim, Se-Jin
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.9 no.1
    • /
    • pp.82-95
    • /
    • 1992
  • There is the high interest for sensing of tool wear with the aim of controlling machine tools productivity from the point of view of qualitity. Difficulties in this measurement are also known. This study is on the development of measurement setup for crater wear by CCD image inturning. In this study, the crater wear measurement system consists of the He-Ne gas laser, diffraction grating. CCD camera, noise filter, slit, microcomputer, diverging lens, converging lens and so on. He-Ne laser beam passes through a diverging lens and a diffraction grating is positioned properly. A converging lens focuses so that the interference fringes can be obtained on the crater wear. Performance test revealed that the developed image technique provides precise, absolute tool-wear quantification and reduces human measurement errors. The results obtained are as follows 1. The digitizing of one image requires less than 2ses. 2. It can give detailed information on crater wear with limited times and errors 3. All parameters required by specification are easily obtained for several points of the cutting edge.

  • PDF

An Implicit Unstructured Finite Element Method for Diffraction of Water Waves by Two-Dimensional Floating Breakwaters (부유체 주위의 2차원 회절 문제를 위한 내율적 비정렬 격자 유한요소해법)

  • 정구창
    • Journal of Ocean Engineering and Technology
    • /
    • v.11 no.4
    • /
    • pp.90-101
    • /
    • 1997
  • A hybrid element method is presented for two-dimensional diffraction problem of water waves. In this method, only a limited fluid domain close to irregular bodies is discretized into conventional finite elements, while the remaining infinite domain is treated as one element with analytical representations of high accuracy. A finite element grid is automatically generated by using Dealunay triangulation based on the Bowyer's algorithm and a linear system of equations is approximately solved with the ILU-CGS algorithm. To validate the present scheme, Computational results are compared with the existing experimental data and other numerical solutions.

  • PDF

Diffraction-Limited High-Power Single-Cycle Terahertz Pulse Generation in Prism-Cut LiNbO3 for Precise Terahertz Applications

  • Baek, In Hyung;Kang, Bong Joo;Jeong, Young Uk;Rotermund, Fabian
    • Journal of the Optical Society of Korea
    • /
    • v.18 no.1
    • /
    • pp.60-64
    • /
    • 2014
  • We report the generation of 3.3-mW single-cycle terahertz (THz) pulses at 1-kHz repetition rate via optical rectification in MgO-doped prism-cut stoichiometric LiNbO3. Efficient pulse-front tilting of 800-nm pulses was realized by an optimized single-lens focusing scheme for radially-symmetric propagation of THz beams. In this geometry, nearly-diffraction-limited THz Gaussian beams with electric field strength as high as 350 kV/cm were generated. The pump-to-THz energy conversion efficiency of $1.36{\times}10^{-3}$ and the extremely high signal-to-noise ratio of ~1:15000 achieved are among the best results for 1-kHz single-cycle terahertz pulse generation ever demonstrated in room temperature operation.