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  • SPIE Digital Library  (32)
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  • SPIE Digital Library  (32)
  • 1
    Language: English
    In: 21 November 2017, Vol.10567, pp.105673D-105673D-7
    Description: The paper gives an overview of the development of a high-performance space structure achieving an optimum combination of mass, stiffness and stability to cope with the very stringent performance requirements of ALADIN instrument, the space-borne LIDAR built for ADM-AEOLUS ESA’s Earth Explorer Mission. Kayser-Threde has been contracted in 2003 by EADS Astrium Toulouse, ALADIN instrument Prime Contractor, for the Phase C/D of ALADIN Structure PFM. The contract with ASF comprised the detailed design, development, verification, PMP qualification, and MAIV program including ALADIN Structure qualification using a complete and fully representative STM.
    Keywords: Engineering
    ISBN: 9781510616233
    ISBN: 1510616233
    ISSN: 0277786X
    E-ISSN: 1996756X
    Source: SPIE Digital Library - Journals
    Source: SPIE Digital Library - Proceedings
    Source: SPIE Digital Library - eBooks
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  • 2
    Language: English
    In: 20 February 2017, Vol.10116, pp.1011603-1011603-8
    Description: Electrostatic actuation is highly efficient at micro and nanoscale. However, large deflection in common electrostatically driven MEMS requires large electrode separation and thus high driving voltages. To offer a solution to this problem we developed a novel electrostatic actuator class, which is based on a force-to-stress transformation in the periodically patterned upper layer of a silicon cantilever beam. We report on advances in the development of such electrostatic bending actuators. Several variants of a CMOS compatible and RoHS-directive compliant fabrication processes to fabricate vertical deflecting beams with a thickness of 30 μm are presented. A concept to extend the actuation space towards lateral deflecting elements is introduced. The fabricated and characterized vertical deflecting cantilever beam variants make use of a 0.2 μm electrode gap and achieve deflections of up to multiples of this value. Simulation results based on an FE-model applied to calculate the voltage dependent curvature for various actuator cell designs are presented. The calculated values show very good agreement with the experimentally determined voltage controlled actuation curvatures. Particular attention was paid to parasitic effects induced by small, sub micrometer, electrode gaps. This includes parasitic currents between the two electrode layers. No experimental hint was found that such effects significantly influence the curvature for a control voltage up to 45 V. The paper provides an outlook for the applicability of the technology based on specifically designed and fabricated actuators which allow for a large variety of motion patterns including out-of-plane and in-plane motion as well as membrane deformation and linear motion.
    Keywords: Engineering
    ISBN: 9781510606739
    ISBN: 1510606734
    ISSN: 0277786X
    E-ISSN: 1996756X
    Source: SPIE Digital Library - Proceedings
    Source: SPIE Digital Library - Journals
    Source: SPIE Digital Library - eBooks
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  • 3
    Language: English
    In: Proceedings of SPIE, 10 March 2011, Vol.7954(1), pp.79540Q-79540Q-8
    Description: Improving the crystal quality of AlGaN epitaxial layers is essential for the realization of efficient III-nitride-based light emitting diodes (LEDs) with emission wavelengths below 365 nm. Here, we report on two different approaches to improve the material quality of AlGaN buffer layers for such UV-LEDs, which are known to be effective for the MOVPE growth of GaN layers. Firstly, we grew AlGaN on thin GaN nucleation islands which exhibit a threedimensional facetted structure (3D GaN nucleation). Lateral overgrowth of these islands results in a lateral bending of dislocation lines at the growing facets. Secondly, in-situ deposited SiN interlayers have been used as nano-masks reducing the dislocation density above the SiN layers. Both approaches result in reduced asymmetric HRXRD -scan peak widths, indicating a reduced edge-type dislocation density. They can be applied to the growth of AlGaN layers with an Al concentration of at least 20%, thus suitable for LEDs emitting around 350 nm. On-wafer electroluminescence measurements at 20 mA show an increase in output power by a factor of 7 and 25 for LED structures grown on 3D GaN nucleation and SiNx interlayer, respectively, compared to structures grown on a purely 2D grown low Al-content AlGaN nucleation layer. Mesa-LEDs fabricated from the LED layer sequences grown on buffers with SiN interlayer exhibit a low forward voltage of 3.8 V at 20 mA and a maximum continuous wave (cw) output power of 12.2 mW at 300 mA.
    Keywords: Engineering
    ISBN: 9780819484918
    ISSN: 0277-786X
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  • 4
    Language: English
    In: 18 February 2004, Vol.5249, pp.165-174
    Description: Pan-STARRS, the Panoramic Survey Telescope and Rapid Response System, is a project to develop a system of four wide field synoptic telescopes. It is designed to accomplish many of the science goals envisioned by the decadal review for LSST. The primary mission of Pan-STARRS is the detection of potentially hazardous asteroids (PHA), secondary science objectives are a (nearly) all-sky survey, a medium-deep survey, an ultra-deep survey, and studies of variability. This paper discusses the basic design choice of a distributed system of four telescopes and the details of the optics design.
    Keywords: Engineering
    ISBN: 9780819451330
    ISBN: 0819451339
    ISSN: 0277786X
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  • 5
    Language: English
    In: 03 March 2003, Vol.4857, pp.239-250
    Description: SUNRISE is a balloon-borne instrument for spectro-polarimetric high-resolution observation of the solar atmosphere. It has a lightweight UV-VIS telescope of Gregory type with an aperture of 1 m, designed to be close to the VIS diffraction limit. The paper will first present the basic prescriptions of the optical design and the achievable performance. The re-quirements for the mechanisms in order to maintain the alignment over the range of environmental conditions will be derived. Secondly, the structural and thermal requirements will be discussed. Here, structural deflections due to gravity and residual thermal imbalances have to be taken into account. Preliminary structural and thermal designs will be out-lined.
    Keywords: Engineering ; Astronomy & Astrophysics
    ISBN: 9780819446367
    ISBN: 081944636X
    ISSN: 0277786X
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  • 6
    Language: English
    In: Proceedings of SPIE, 12 April 2001, Vol.4347(1), pp.13-16
    Description: An example of a multilayer component for 248-nm excimer laser applications is explained in this contribution. By means of a polarizing beam splitter the potential of plasma- assisted deposition is shown. Such a coating shows a high reflecting and a high transmitting function for different polarization at a certain angle of incidence. High reflection requires a considerable number of layer pairs with a large total optical film thickness. Despite large film thickness, the optical absorption can be minimized and high transmission can be obtained. The laser induced damage threshold of such a coating is in the order of 2.5 J/cm for single shot measurements at 20 ns pulse length. The life time is greater than 5X10 shots at a fluence of 10mJ/cm . Very stable deposition conditions must be maintained to produce these coatings within small tolerance of the optical function. It was found that plasma-assisted deposition is a more reliable technology for producing these coatings compared to classical evaporation.
    Keywords: Engineering
    ISBN: 9780819440365
    ISSN: 0277-786X
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  • 7
    Language: English
    In: Proceedings of SPIE, 30 September 2005, Vol.5962(1), pp.59620R-59620R-12
    Description: Triggered by the roadmap of the semiconductor industry, tremendous progress has been achieved in the development of Extreme Ultraviolet (EUV) sources and high-quality EUV optical coatings in recent years, opening up also new fields of applications apart from microlithography, such as metrology, high-resolution microscopy, or surface analysis. In all these research areas the quality and imaging properties of the employed optics play a crucial role. In this contribution we present a comparison of different optical setups capable of guiding and imaging EUV radiation, which were tested in combination with a miniaturized laser-produced plasma source with high pulse energy (~ 3.5 mJ @ 13.5 nm) and a plasma size of about 300 m. First, a modified EUV Schwarzschild objective with a numerical aperture of 0.44 and a demagnification factor of 10 was developed within the research project "KOMPASS". After adaptation to the table-top EUV source, a focus with a diameter 〈 30 m at energy densities of several mJ/cm could be produced. The setup is currently being used for comparative investigations of the interaction of EUV radiation with different materials, as e.g. the color center formation in LiF crystals. An attempt to use the Schwarzschild objective in reverse geometry as a EUV microscope will be part of future work. Second, a Kirkpatrick-Baez arrangement was realized, using the reflections from two curved silicon wafers under grazing incidence (about 5°). The cylindrical curvature is obtained by bending the thin substrates, allowing for a continuous tuning to the desired radii. Due to an Au coating a high reflectivity (theoretically ~ 80 % per reflection) over a broad EUV spectral range can be achieved. For reduction of aberrations the optical systems were fine-adjusted with the help of a Hartmann-Shack wavefront sensor both in the visible and in the EUV spectral range. The imaging properties in the EUV range were determined and compared to ray tracing calculations performed with ZEMAX.
    Keywords: Engineering
    ISSN: 0277-786X
    Source: SPIE Digital Library - Journals
    Source: SPIE Digital Library - Proceedings
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  • 8
    Language: English
    In: 02 February 2004, Vol.5234, pp.221-231
    Description: The high resolution airborne imaging spectrometer APEX (Airborne Prism Experiment) is currently being built. In parallel, its data processing calibration chain is being designed. The complex design of this high resolution pushbroom instrument bears the risk of optical aberrations in the registered spatio-spectral frames. Such aberrations consist of so-called frown and smile effects, as well as ghost image, smear, and stray light contributions. A concept is presented which shall operationally improve image calibration by inversion of the sensor model.
    Keywords: Engineering
    ISBN: 9780819451170
    ISBN: 0819451177
    ISSN: 0277786X
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  • 9
    Language: English
    In: Proceedings of SPIE, 04 November 2004, Vol.5570(1), pp.445-452
    Description: APEX is a dispersive pushbroom imaging spectrometer operating in the spectral range between 380 - 2500 nm. The spectral resolution will be better than 10 nm in the SWIR and 〈 5 nm in the VNIR range of the solar reflected range of the spectrum. The total FOV will be ± 14 deg, recording 1000 pixels across track with about 300 spectral bands simultaneously. A large variety of characterization measurements will be performed in the scope of the APEX project, e.g., on-board characterization, frequent laboratory characterization, and vicarious calibration. The retrieved calibration parameters will allow a data calibration in the APEX Processing and Archiving Facility (PAF). The data calibration includes the calculation of the required, time-dependent calibration coefficients from the calibration parameters and, subsequently, the radiometric, spectral and geometric calibration of the raw data. Because of the heterogeneity of the characterization measurements, the optimal calibration for each data set is achieved using a special assimilation algorithm. In the paper the different facilities allowing characterization measurements, the PAF and the new data assimilation scheme are outlined.
    Keywords: Engineering
    ISBN: 9780819455178
    ISSN: 0277-786X
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  • 10
    Language: English
    In: 02 February 2004, Vol.5234, pp.211-220
    Description: The underlying algorithmic architecture of the level 0 to 1 processing of the APEX spectrometer is presented. This processing step calculates the observed radiances in physical units from the recorded raw digital numbers. APEX will operate airborne and record radiance in the solar reflected wavelength range. The system is optimized for land applciations including limnology, snow, soil, amongst others. The instrument will be calibrated with a flexible setup in a laboratory as well as on-board. A concept for the dynamic update of the radiance calibration coefficients for the APEX spectrometer is presented. The time evolution of the coefficients is calculated from the heterogeneous calibration measurements with a data assimilation technique. We propose a Kalman filter for the initial version of the processor. Additionally, the structure of the instrument model suitable for the analysis of APEX data is developed. We show that this model can be used for the processing of observations as well as for the calculation of calibration coefficients. Both processes can be understood as inverse problems with the same forward model, i.e. the instrument model.
    Keywords: Engineering
    ISBN: 9780819451170
    ISBN: 0819451177
    ISSN: 0277786X
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