• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 21
  • 7
  • 5
  • 3
  • 2
  • 2
  • 1
  • Tagged with
  • 42
  • 42
  • 10
  • 7
  • 7
  • 6
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Observational Studies of Interacting Galaxies and the Development of the Wide Integral Field Infrared Spectrograph

Chou, Chueh-Yi 19 March 2013 (has links)
Interacting galaxies are thought to be the essential building blocks of elliptical galaxies under the hierarchical galaxy formation scenario. The goal of my dissertation is to broaden our understanding of galaxy merger evolution through both observational studies and instrument developments. Observationally, I approach the goal photometrically and spectroscopically. The photometric studies better constrain the number density evolution of wet and dry mergers through five CFHTLS broad band photometry up to z~1. Meanwhile, by comparing the merger and elliptical galaxy mass density function, I discovered that the most massive mergers are not all formed via merging processes, unless the merging timescale is much longer than the expected value. Spectroscopically, the kinematic properties of close pair galaxies were studied to understand how star formation were quenched at z~0.5. I discovered that the number of red-red pairs are rare, which does not support the gravitational quenching mechanism suggested by the hot halo model. In instrumentation, one efficient way to study galaxy mergers is to use the integral field spectroscopic technique, capitalizing its intrinsic capability of obtaining 2-D spectra effectively. However, the currently available integral field spectrographs are inadequate to provide the required combination of integral field size and spectral resolution for merger studies. I, therefore, have developed two optical designs of a wide integral field infrared spectrograph (WIFIS), which I call WIFIS1 and WIFIS2, to satisfy the requirements of merger studies. Both the designs provide an integral field of 12" x 5" on 10-m telescopes (or equivalently 52" x 20" on 2.3-m telescopes). WIFIS1 delivers spectral resolving powers of 5,500 covering each of JHK bands in a single exposure; WIFIS2 does a lower power of 3,000 focusing on a shorter wavebands of zJ and H bands. All the WIFIS2 optical components have either been or being fabricated, and some of the components have been characterized in the laboratory, including its integral field unit, gratings, and mirrors. The expected completion of WIFIS based on WIFIS2 is 2013 summer, which will be followed by WIFIS1-based spectrograph in a few years.
2

Observational Studies of Interacting Galaxies and the Development of the Wide Integral Field Infrared Spectrograph

Chou, Chueh-Yi 19 March 2013 (has links)
Interacting galaxies are thought to be the essential building blocks of elliptical galaxies under the hierarchical galaxy formation scenario. The goal of my dissertation is to broaden our understanding of galaxy merger evolution through both observational studies and instrument developments. Observationally, I approach the goal photometrically and spectroscopically. The photometric studies better constrain the number density evolution of wet and dry mergers through five CFHTLS broad band photometry up to z~1. Meanwhile, by comparing the merger and elliptical galaxy mass density function, I discovered that the most massive mergers are not all formed via merging processes, unless the merging timescale is much longer than the expected value. Spectroscopically, the kinematic properties of close pair galaxies were studied to understand how star formation were quenched at z~0.5. I discovered that the number of red-red pairs are rare, which does not support the gravitational quenching mechanism suggested by the hot halo model. In instrumentation, one efficient way to study galaxy mergers is to use the integral field spectroscopic technique, capitalizing its intrinsic capability of obtaining 2-D spectra effectively. However, the currently available integral field spectrographs are inadequate to provide the required combination of integral field size and spectral resolution for merger studies. I, therefore, have developed two optical designs of a wide integral field infrared spectrograph (WIFIS), which I call WIFIS1 and WIFIS2, to satisfy the requirements of merger studies. Both the designs provide an integral field of 12" x 5" on 10-m telescopes (or equivalently 52" x 20" on 2.3-m telescopes). WIFIS1 delivers spectral resolving powers of 5,500 covering each of JHK bands in a single exposure; WIFIS2 does a lower power of 3,000 focusing on a shorter wavebands of zJ and H bands. All the WIFIS2 optical components have either been or being fabricated, and some of the components have been characterized in the laboratory, including its integral field unit, gratings, and mirrors. The expected completion of WIFIS based on WIFIS2 is 2013 summer, which will be followed by WIFIS1-based spectrograph in a few years.
3

OPTIMIZATION AND EVALUATION OF MANUFACTURING TOLERANCES OF A THREE-MIRROR ASPHERIC CAMERA

Van Workum, John A. 15 January 1971 (has links)
QC 351 A7 no. 61 / In an attempt to design a three -mirror aspheric camera, a procedure was developed to arrive at a design with a minimum obscuration ratio. It was found that, in some cases, the sky baffling became the diffracting obscuration rather than the obscuration caused by the secondary. The procedure allowed for this and was able to select a system with the smallest diffracting obscuration in the pupil. Initially, two designs were selected and optimized through the use of aspheric surfaces. The designs represented two extremes in that one had much faster surfaces than the other. The fast mirror system was easier to optimize, performed better, and had the shorter over -all length. Further, evaluation of manufacturing errors on the fast mirror design showed that an acceptable level of performance could be expected if the errors were kept small. The maximum errors are spacing errors ±0.0005 in. tilt of surface errors ±0.001 /D in. radii of curvature errors ±0.125 in. where D is the diameter of the mirror surface.
4

Focused ion beam direct fabrication of micro-optical elements: features compared with laser beam and electron beam direct writing

Fu, Yongqi, Ngoi, Kok Ann Bryan 01 1900 (has links)
Three types of focused ion beam machine: focused ion beam milling (FIB milling), focused ion beam lithography (FIB lithography), and focused ion beam direct deposition (FIB deposition), are described in detail to compare with electron beam lithography (EBL) and laser beam direct writing (LBW). A diffractive optical element (DOE) with continuous relief, six-annulus, relief depth of 1.17µm, and diameter of 65 µm, fabricated by use of the FIB milling, is cited as an example to illustrate the FIB milling and the comparison with the EBL and the LBW. Micro-cylindrical lens with dimension of 2.8µm×7.5µm×0.95µm in width, length and height, NA=0.2, is given as another fabrication example to illustrate the FIB deposition, which is a unique function for all the direct writing methods. They are all superiors to the EBL and the LBW in the case that optical elements need to be directly fabricated in local area of a device. / Singapore-MIT Alliance (SMA)
5

Optical design for the large balloon reflector

Cortes-Medellin, German, O'Dougherty, Stefan, Walker, Christopher, Goldsmith, Paul F., Groppi, Chris, Smith, Steve, Bernasconi, Pietro 27 July 2016 (has links)
We present the details of the optical design, corrector system, mechanical layout, tolerances, pointing requirements, and overall performance of the sub-millimeter wavelength Large Balloon Reflector telescope (LBR).
6

Design and Development of Compact Multiphoton Microscopes

Mehravar, SeyedSoroush, Mehravar, SeyedSoroush January 2016 (has links)
A compact multi-photon microscope (MPM) was designed and developed with the use of low-cost mode-locked fiber lasers operating at 1040nm and 1560nm. The MPM was assembled in-house and the system aberration was investigated using the optical design software: Zemax. A novel characterization methodology based on 'nonlinear knife-edge' technique was also introduced to measure the axial, lateral resolution, and the field curvature of the multi-photon microscope's image plane. The field curvature was then post-corrected using data processing in MATLAB. A customized laser scanning software based on LabVIEW was developed for data acquisition, image display and controlling peripheral electronics. Finally, different modalities of multi-photon excitation such as second- and third harmonic generation, two- and three-photon fluorescence were utilized to study a wide variety of samples from cancerous cells to 2D-layered materials.
7

Optical Design And Analysis Of A Riflescope System

Bayar, Cevdet 01 September 2009 (has links) (PDF)
Today, riflescope systems are used widely, mostly by military forces. In this study, a riflescope working in the visible range (400-700 nm) will be designed. The riflescope will have 3 degrees field of view and maximum 15 cm total track. Total design length is limited to 15 cm because a short riflescope is more stabilized than a long one with respect to thermal instability and vibrational effects. Taken into account the cost factor, only two types of glasses will be used in the design. One of them is NBK7 a crown glass and the other is N-F2 a flint glass. Moreover, Schmidt-Pechan prism will be used to construct an erected image. The optical performance analysis of the design is also carried out for a production ready riflescope system.
8

Short Wave Infrared Camera Design And Focal Plane Analysis

Bolat Beldek, Tugba 01 February 2012 (has links) (PDF)
The subject of this study is the design of a camera, which has maximum volume of 50 mm x 50 mm x 300 mm, using short infrared wavelength providing Rayleigh criteria. Firstly, the required flux per pixel has been calculated. Throughout these calculations, atmospheric losses have been obtained by MODTRAN program. Also signal to noise ratio has been examined at minimum and maximum integration time intervals. The focal length of the camera has been calculated as it receives 1 m resolution from 8 km distance. Moreover, the lens materials have been used as N-F2, LIF and BaF2 in this six lens system. The design has been done using ZEMAX optical design program and the performance of the system at focal plane was investigated by the help of Seidel aberrations, Modulation transfer Function (MTF), Spot diagram and Optical Path Difference (OPD) fan plot analyses.
9

High Numerical Aperture Injection-Molded Miniature Objective For Fiber-Optic Confocal Reflectance Microscopy

Chidley, Matthew D. January 2005 (has links)
This dissertation presents the design of a miniature injection-molded objective lens for a fiber-optic confocal reflectance microscope. This is part of an effort to demonstrate the ability to fabricate low cost, high performance biomedical optics for high resolution in vivo imaging. Disposable endoscopic microscope objectives could help in vivo confocal microscopy technology mature to enable large-scale clinical screening and detection of early cancers and pre-cancerous lesions. This five lens plastic objective has been tested as a stand-alone optical system and has been coupled to a confocal microscope for in vivo imaging of cells and tissue. Changing the spacing and rotation of the individual optical elements can compensate for fabrication inaccuracies and improve performance. An optical-bench testing system was constructed to allow interactive alignment during testing. The modulation transfer function (MTF) of the miniature objective lens is determined using the slanted-edge method. A custom MATLAB program, edgeMTF, was written to collect, analyize, and record test data. An estimated Strehl ratio of 0.64 and an MTF value of 0.70, at the fiber-optic bundle Nyquist frequency, have been obtained. The main performance limitations of the miniature objective are mechanical alignment and flow-induced birefringence. Annealing and experimental injection molding runs were conducted in effort to reduce birefringence.
10

A method for the design of unsymmetrical optical systems using freeform surfaces

Reshidko, Dmitry, Sasian, Jose 27 November 2017 (has links)
A systematic method for the design of unsymmetrical optical systems is described. Freeform optical surfaces are constructed by superposition of a conic segment and a polynomial, and successfully applied to design relatively fast wide field-of-view optical systems.

Page generated in 0.0646 seconds