• Title/Summary/Keyword: Beam focusing

Search Result 253, Processing Time 0.034 seconds

Tool Fracture Detection by End Mill Deflection (엔드밀 변위에 의한 공구파손검출)

  • 맹민재
    • Journal of the Korean Society of Manufacturing Technology Engineers
    • /
    • v.8 no.2
    • /
    • pp.100-107
    • /
    • 1999
  • End milling experiments are conducted to investigate characteristics of laser beam signals due to tool fracture. The laser beam signals are obtained with adapt focusing of tool. Tool states are identified wit h scanning electron microscopy and optical microscopy. It is demonstrated that the laser beam signals provide reliable informations about the cutting processes and tool states. Moreover, tool fracture can be detected successfully using coefficient of variation.

  • PDF

Active Focusing of Light in Plasmonic Lens via Kerr Effect

  • Nasari, Hadiseh;Abrishamian, Mohammad Sadegh
    • Journal of the Optical Society of Korea
    • /
    • v.16 no.3
    • /
    • pp.305-312
    • /
    • 2012
  • We numerically demonstrate the performance of a plasmonic lens composed of an array of nanoslits perforated on thin metallic film with slanted cuts on the output surface. Embedding Kerr nonlinear material in nanoslits is employed to modulate the output beam. A two dimensional nonlinear-dispersive finite-difference time-domain (2D N-D-FDTD) method is utilized. The performance parameters of the proposed lens such as focal length, full-width half-maximum, depth of focus and the efficiency of focusing are investigated. The structure is illuminated by a TM-polarized plane wave and a Gaussian beam. The effect of the beam waist of the Gaussian beam and the incident light intensity on the focusing effect is explored. An exact formula is proposed to derive electric field E from electric flux density D in a Kerr-Dispersive medium. Surface plasmon (SPs) modes and Fabry-Perot (F-P) resonances are used to explain the physical origin of the light focusing phenomenon. Focused ion beam milling can be implemented to fabricate the proposed lens. It can find valuable potential applications in integrated optics and for tuning purposes.

Hollow Beam Atom Tunnel (속 빈 레이저 빔을 이용한 원자 가이드)

  • 송연호
    • Proceedings of the Optical Society of Korea Conference
    • /
    • 2000.02a
    • /
    • pp.130-131
    • /
    • 2000
  • One of the more promising proposals for guiding and focusing neutral atoms involves dark hollow laser beams. When the frequency of the laser is detuned to the blue of resonance, the dipole force the atoms feel in the light confines them to the dark core where the atoms can be transported with minimal interaction with the light. The ability of the all-light atom guides to transport large number of ultracold atoms for long distances without physical walls leads to the possibility of a versatile tool for atom lithography, atom interferometry, atomic spectroscopy as well as for transporting and manipulating Bose-Einstein condensates. Furthermore since the atoms transported in all-light atom guides do not come into contact with matter, they can in principle be used to transport antimatter as well. The ability to vary the core size of the hollow beam makes the all-light atom guide potentially useful for focusing neutral atoms. The atoms could be focused as tight as the core size of the hollow beam at its waist. This new focusing scheme, called the atom funnel, would not show spherical and chromatic aberrations that conventional harmonic focusing suffers from. (omitted)

  • PDF

x$^{(3)}$ Measurement through Self-focusing with Non-gaussian Beam (비 Gaussian 빛에 의한 자체집광을 이용한 x$^{(3)}$측정)

  • 이범구
    • Korean Journal of Optics and Photonics
    • /
    • v.4 no.4
    • /
    • pp.428-433
    • /
    • 1993
  • The second harmonic of Q-switched Nd:YAG laser beam with gaussian mode is cut off by pinhole of a certain radius and its central portion passed through pinhole is focused by converging lens. It is confirmed that the shape of this beam in focal region is central symmetric but non-gaussian. Change of transmittance due to self-focusing is investigated by scanning (z-scan) $CS_2$ of 1 mm thickness in the focal region. It is found that the observed results can be consistently explained by Fresnel theory within 1.5% accuracy and efficiency of self-focusing depends on spatial shape of incident beam.

  • PDF

Model for the Inertial Focusing of Particles Using an Atmospheric Aerodynamic Lens (상압 공기역학적 렌즈의 입자 관성집속 모델)

  • Lee, Jin-Won;Lee, Min-Yeong
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.25 no.3
    • /
    • pp.315-321
    • /
    • 2001
  • Aerodynamic lenses are widely used in generating particle beams of high density and small diameter, but analytical or modeling studies are limited only in the free molecular regime. In this study, it is shown that generating particle beam is also possible in atmospheric pressure range, and the mechanism of generating particle beam using an orifice is analysed into three different parts : fluid dynamic contraction, diffusional defocusing, and inertial focusing. In laminar flow conditions, the diffusional defocusing effect can be neglected, and the effects of inertial focusing can be expressed in terms of the orifice size and Stokes number. Numerical experiments are done for two different orifices, d/D=1/5 and 1/10 and particle diameter d(sub)p=1-10 ㎛. The results for two different orifices can be made into a single curve when a modified Stokes number is used. The inertial focusing effect diminishes when the modified Stokes number becomes smaller than 10(sup)-2.

Development of an Auto Sample Centering Algorithm at the Macromolecular Crystallography Beam Line of the Pohang Light Source (단백질 결정학 빔 라인에서의 자동 샘플 정렬 알고리즘 개발)

  • Jang, Yu-Jin
    • The Transactions of the Korean Institute of Electrical Engineers D
    • /
    • v.55 no.7
    • /
    • pp.313-318
    • /
    • 2006
  • An automatic sample centering system is underway at the protein crystallography beam line of the Pohang Light Source to improve the efficiency of the crystal screening process. A sample pin which contains a protein crystal is mounted on a goniometer head. Then the crystal should be moved to the center of X-ray beam by controlling the motorized goniometer to obtain diffraction data. Since the X-ray beam is located at the center of the image obtained from the CCD camera when the image of the sample pin is in focus, an auto-focusing algorithm is a very important part in the auto-sample-centering system. However the results of applying several well-known auto focusing algorithms directly to the images are not satisfactory owing to the following factors: misalignment of CCD camera, non-uniform cryo-stream in the background of the image and the supporter of the loop. The performance of an auto-focusing algorithm can be increased if the algorithm is applied to only the loop region identified. Non-uniform cryo-stream and a various illumination condition and a stain, which is shown in the image, are main obstacles to loop region identification. In this paper, a simple loop region identification algorithm, which can solve these problems, is proposed and the effective ness of the proposed scheme is shown by applying the auto-focusing algorithm to the loop region identified.

A Study on the Influence of Pure Iron Purity of Electric Lens on the Electron Beam Control (전자빔 가공기의 전자렌즈 순철순도가 빔 제어에 미치는 영향)

  • Lee Chan-Hong;Ro Seung-Kook
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • 2005.10a
    • /
    • pp.149-153
    • /
    • 2005
  • The electron beam machining provides very high resolution up to nanometer scale, hence the E-beam writing technology is rapidly growing in MEMS and nano-engineering areas. In the optical column of the e-beam writer, there are several lenses condensing and focusing electron beams from electron gun with fringing magnetic fields. The polepieces of these lenses are usually made with high purity iron which is hard to fabricate and very expensive. In this paper, the possibility of using polepiece of object lens composed with pure iron and low carbon steel was examined to reduce cost. The magnetic field at object lens was calculated with finite element method, and practical focusing qualities of SEM pictures were observed comparing for the object lens polepieces with pure iron and two type of composed with low carbon steel.

  • PDF

Time Reversal Focusing and Imaging of Point-Like Defects in Specimens with Nonplanar Surface Geometry

  • Jeong, Hyun-Jo;Lee, Hyun-Kee;Bae, Sung-Min;Lee, Jung-Sik
    • Journal of the Korean Society for Nondestructive Testing
    • /
    • v.30 no.6
    • /
    • pp.569-577
    • /
    • 2010
  • Nonplanar surface geometries of components are frequently encountered in real ultrasonic inspection situations. Use of rigid array transducers can lead to beam defocusing and reduction of defect image quality due to the mismatch between the planar array and the changing surface. When a flexible array is used to fit the complex surface profile, the locations of array elements should be known to compute the delay time necessary for adaptive heam focusing. An alternative method is to employ the time reversal focusing technique that does not require a prior knowledge about the properties and structures of the specimen and the transducer. In this paper, a time reversal method is applied to simulate beam focusing of flexible arrays and imaging of point-like defects contained in specimens with nonplanar surface geometry. Quantitative comparisons are made for the performance of a number of array techniques in terms of the ability to focus and image three point-like reflectors positioned at regular intervals. The sinusoidal profile array studied here exhibits almost the same image quality as the flat, reference case.

A Concept of Adaptive Focusing using a Rotman Lens for Detecting Buried Structures

  • Kim, Jae-Heung
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
    • /
    • 2003.11a
    • /
    • pp.536-540
    • /
    • 2003
  • A new concept of adaptive focusing, using a Rotman lens, is presented in this paper. A Rotman lens is a microwave lens which is able to focus microwave power on its focal arc or generate multiple beams. By adding the array of phase shifters between a Rotman lens and antenna elements, the wavefront can be adaptively modulated to focus objects distributed in short range rather than far-field zone. From the optical point of view, the propagations of the lens have been simplified from the Fresnel diffraction integral to the Fourier transform. Using Fourier Transform, a beam propagation method has been developed to show improvement of the resolution by controlling wavefront of wave propagating from an aperture-type antenna array. The beam width(or spot size) and intensity have been calculated for a focused beam propagating from an array having $10{\lambda}$ of its size. For the beam with $20{\lambda},\;30{\lambda}$, and $50{\lambda}$ of geometrical focal length, the half-power beamwidth (spot size) is about $1.1{\lambda},\;1.3{\lambda}$, and $1.9{\lambda}$, respectively.

  • PDF

Fabrication technology of the focusing grating coupler using single-step electron beam lithography (Single-step 전자빔 묘화 장치를 이용한 Focusing Grating Coupler 제작 연구)

  • Kim, Tae-Youb;Kim, Yark-Yeon;Sohn, Yeung-Joon;Han, Gee-Pyeong;Paek, Mun-Cheol;Kim, Hae-Sung;Shin, Dong-Hoon;Rhee, Jin-Koo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • 2002.07b
    • /
    • pp.976-979
    • /
    • 2002
  • A focusing grating coupler (FGC) was not fabricated by the 'Continuous Path Control' writing strategy but by an electron-beam lithography system of more general exposure mode, which matches not only the address grid with the grating period but also an integer multiple of the address grid resolution (5 nm), To more simplify the fabrication, we are able to reduce a process step without large decrease of pattern quality by excluding a conducting material or layer such as metal (Al, Cr, Au), which are deposited on top or bottom of an e-beam resist to prevent charge build-up during e-beam exposure. A grating pitch period and an aperture feature size of the FGC designed and fabricated by e-beam lithography and reactive ion etching were ranged over 384.3 nm to 448.2 nm, and $0.5{\times}0.5mm^2$ area, respectively, This fabrication method presented will reduce processing time and improve the grating quality by means of a consideration of the address grid resolpution, grating direction, pitch size and shapes when exposing. Here our investigations concentrate on the design and efficient fabrication results of the FGC for coupling from slab waveguide to a spot in free space.

  • PDF