65 results on '"Chang Jin Oh"'
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2. The Large Fiber Array Spectroscopic Telescope: fiber feed and spectrometer conceptual design
- Author
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Chad F. Bender, Roger Angel, Joel Berkson, Peter Gray, Samuel Halverson, Hyukmo Kang, Daewood Kim, Andrew Monson, Chang Jin Oh, Matthew Rademacher, Christian Schwab, Andrew Young, and Dennis Zaritsky
- Published
- 2022
3. LFAST, the Large Fiber Array Spectroscopic Telescope
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J. Roger Angel, Chad F. Bender, Joel Berkson, Nick Didato, John Ford, Peter Gray, Buell Jannuzi, Dean Ketelsen, Daewook Kim, Gilberto Chavez Lopez, Andrew Monson, Chang-Jin Oh, Jason Patrou, Matthew Rademacher, Christian Schwab, Melanie Sisco, Rich Wortley, and Andrew J. Young
- Published
- 2022
4. The large fiber array spectroscopic telescope: opto-mechanical design and architecture
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Andrew J. Young, J. Roger Angel, Chad F. Bender, Joel Berkson, Peter Gray, Samuel Halverson, Hyukmo Kang, Daewook Kim, Andy Monson, Chang-Jin Oh, Matthew Rademacher, Christian Schwab, and Dennis Zaritsky
- Published
- 2022
5. The Relationship between Socially Prescribed Perfectionism and Academic Stress in College Students: The Moderated Mediating Effects of Self-Soothing Ability through Post-Event Rumination
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Chang Jin Oh, Wonyoung Song, and Yo Han Kang
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Self soothing ,Event (relativity) ,Rumination ,Stress (linguistics) ,medicine ,General Medicine ,Perfectionism (psychology) ,medicine.symptom ,medicine.disease_cause ,Psychology ,Developmental psychology - Published
- 2020
6. Modal Data Processing for High Resolution Deflectometry
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Chang Jin Oh, Dae Wook Kim, Maham Aftab, Logan R. Graves, Greg Smith, and James H. Burge
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0209 industrial biotechnology ,Polynomial ,Chebyshev polynomials ,Renewable Energy, Sustainability and the Environment ,Computer science ,Mechanical Engineering ,Scalar (physics) ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Industrial and Manufacturing Engineering ,Solar telescope ,law.invention ,Primary mirror ,Telescope ,Polynomial basis ,020901 industrial engineering & automation ,law ,Management of Technology and Innovation ,General Materials Science ,Vector field ,0210 nano-technology ,Algorithm - Abstract
In this paper, we present a modal data processing methodology, for reconstructing high resolution surfaces from measured slope data, over rectangular apertures. One of the primary goals is the ability to effectively reconstruct deflectometry measurement data for high resolution and freeform surfaces, such as telescope mirrors. We start by developing a gradient polynomial basis set which can quickly generate a very high number of polynomial terms. This vector basis set, called the G polynomials set, is based on gradients of the Chebyshev polynomials of the first kind. The proposed polynomials represent vector fields that are defined as the gradients of scalar functions. This method yields reconstructions that fit the measured data more closely than those obtained using conventional methods, especially in the presence of defects in the mirror surface and physical blockers/markers such as fiducials used during deflectometry measurements. We demonstrate the strengths of our method using simulations and real metrology data from the Daniel K. Inouye Solar Telescope (DKIST) primary mirror.
- Published
- 2019
7. Reconfigurable dynamic optical system design, test, and data analysis
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Isaac Trumper, Hyemin Yoo, Matthew B. Dubin, Christian Davila-Peralta, Maham Aftab, Dae Wook Kim, Hyukmo Kang, Greg Smith, Henry Quach, Chang-Jin Oh, Justin Hyatt, Heejoo Choi, Andrew E. Lowman, and Logan R. Graves
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Lens (optics) ,Set (abstract data type) ,Chebyshev polynomials ,Polynomial ,Fitness function ,law ,Computer science ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Process (computing) ,Electronic engineering ,Systems design ,law.invention ,Metrology - Abstract
Reconfigurable freeform optical systems enable greatly enhanced imaging and focusing performance within nonsymmetric, compact, and ergonomic form factors. In this paper, several improvements are presented for the design, test, and data analysis with these systems. Specific improvements include definition of a modal G and C vector basis set based on Chebyshev polynomials for the design and analysis of non-circular optical systems. This framework is then incorporated into a parametric optimization process and tested with the Tomographic Ionized-carbon Mapping Experiment (TIME), a reconfigurable optical system. Beyond design, a reconfigurable deflectometry system enhances metrology to measure a fast, f/1.26 convex optic as well as an Alvarez lens. Further improvements in an infrared deflectometry system show accuracy around λ/10 of the notoriously difficult low-order power. Working together, the mathematical vector polynomial set, the programmatic optical design approach, and various deflectometry-based optical testing technologies enable more flexible and optimal utilization of freeform optical components and design configurations.
- Published
- 2020
8. High contrast thermal deflectometry using long-wave infrared time modulated integrating cavity source
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Dae Wook Kim, Logan R. Graves, Henry Quach, R. John Koshel, and Chang Jin Oh
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Resistive touchscreen ,White light interferometry ,Materials science ,Infrared ,Heating element ,business.industry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Signal ,Atomic and Molecular Physics, and Optics ,010309 optics ,Optics ,Radiant flux ,0103 physical sciences ,Thermal ,Black-body radiation ,0210 nano-technology ,business - Abstract
We introduce a scalable temporally modulated long-wave infrared source design. The design makes use of an array of resistive blackbody heating elements which radiate into a custom aluminum integrating cavity. The output of the box is a rectangular slit, built to match the traditional tungsten ribbon profile for an infrared deflectometry source. Temporal modulation allows for signal isolation and improved resilience to background fluctuations in an infrared deflectometry source. Infrared deflectometry measurements using the new source design and a traditional tungsten ribbon, both with similar radiant flux, were compared for a ground glass surface, an aluminum blank, and an aluminum blank under thermal load (150 °C). Signal-to-noise ratio was ∼4 times higher for the new design and demonstrated improved source temporal stability and geometry. Further, the new design successfully measured the previously untestable hot aluminum flat. The new design improves infrared deflectometry and allows for high contrast thermal deflectometry measurements of optics under thermal load.
- Published
- 2019
9. Occupant injury risk analysis at NASS/CDS database
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Hyung Yun Choi, Jin Ho Bae, Jaeho Shin, and Chang Jin Oh
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Thorax ,050210 logistics & transportation ,Database ,business.industry ,05 social sciences ,Steering wheel ,computer.software_genre ,medicine.disease ,Steering column ,law.invention ,Hybrid III ,medicine.anatomical_structure ,law ,0502 economics and business ,Automotive Engineering ,Concussion ,Seat belt ,medicine ,Abdomen ,0501 psychology and cognitive sciences ,Body region ,business ,human activities ,computer ,050107 human factors - Abstract
Injury information for vehicle occupants from the body regions of the head, thorax, abdomen, and upper and lower extremities, due to the restraints and interior parts of the vehicle, were extracted from the 2009 ~ 2012 NASS/CDS database. For those cases with high occurrence frequency, a detailed and comprehensive data analysis was performed to find the relationship between the accident, occupant, vehicle, and injury data. A numerical frontal impact sled model with the Hybrid III dummy and the GHBMC human body model was constructed to simulate and identify those injury risks according to NASS/CDS. Among the 5,734 injuries to the aforementioned body regions from frontal crashes are, listed by frequency of occurrence, the lower extremity (27.8 %), upper extremity (21.3 %), thorax (15.1 %), face (10.9 %), spine (8.7 %), head (7.3 %), and abdomen (6.9 %). The main injury sources to the head were the windshield, side structure, and steering wheel. For the thorax and abdomen they were the seat belt and steering wheel. For the lower extremity it was the instrument panel. The main injury patterns for the head were the concussion and the contusion. For the thorax they were vessel laceration and lung contusion. For the abdomen they were laceration and contusion of the organs. For the lower extremity they were bone fracture and ligament rupture. The steering wheel and seat positions were main factors affecting head and thorax injury risks. From the sled impact simulation, high injury risks of the head and thorax were assessed respectively at conditions of steering column tilt down and rear most seat position, which correlated well with the findings from the NASS/CDS data analysis.
- Published
- 2017
10. Fabrication and Measurement of Large Scale Freeform Optics
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Isaac Trumper, Andrew E. Lowman, Logan R. Graves, Heejoo Choi, Chang Jin Oh, Dae Wook Kim, Maham Aftab, Brian Kellermeyer, and Lei Huang
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Radio telescope ,Fabrication ,Optics ,Scale (ratio) ,business.industry ,Optical testing ,Computer science ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Overall performance ,business ,ComputingMethodologies_COMPUTERGRAPHICS - Abstract
Utilizing freeform optics in an optical system improves the system’s overall performance and form-factor. These benefits come at a cost, both financial and technical, as freeform optics require advanced design, fabrication, and testing methods.
- Published
- 2019
11. Advances in reconfigurable optical design, metrology, characterization, and data analysis
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Henry Quach, Chang Jin Oh, Isaac Trumper, Christian Davila-Peralta, Greg Smith, Andrew E. Lowman, Dae Wook Kim, Heejoo Choi, Maham Aftab, Hyukmo Kang, Logan R. Graves, Hyemin Yoo, Justin Hyatt, and Matt Dubin
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Chebyshev polynomials ,Computer science ,Parametric optimization ,Electronic engineering ,Electrical and Electronic Engineering ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Characterization (materials science) ,Metrology - Abstract
Reconfigurable freeform optical systems greatly enhance imaging performance within non-symmetric, compact, and ergonomic form factors. In this paper, several advances improve design, testing, and monitoring of these systems. Specific enhancements include definition of polynomials for fast and efficient parameterizations of vector distributions in non-circular apertures and merit based function optimization. Deflectometry system improvements enable metrology for almost any conceivable optic shape and guide deterministic optical figuring process during the coarse grinding phase by including modulated infrared sources. As a demonstration of these improvements, parametric optimization is tested with the tomographic ionized-carbon mapping experiment, a reconfigurable optical system. Other case studies and demonstrations include metrology of a fast, f/1.26 convex optic, an Alvarez lens, and real-time monitoring of an array of independently-steerable hexagonal mirror segments as well as an induction formed surface and inflatable Mylar mirror.
- Published
- 2021
12. Improvements in the scanning long-wave optical test system
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Andrew E. Lowman, Hyemin Yoo, Matthew B. Dubin, Chang Jin Oh, and Greg Smith
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Figuring ,Materials science ,Fabrication ,business.industry ,Process (computing) ,Polishing ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Metrology ,Grinding ,010309 optics ,Interferometry ,Optics ,Laser tracker ,0103 physical sciences ,0210 nano-technology ,business - Abstract
The Scanning Long-wave Optical Test System (SLOTS) is a slope measuring deflectometry system that provides accurate measurements on ground surfaces. As it uses a thermal source, we can measure an optic during the grinding phase which allows us to correct figure errors when material removal is much faster. We have made improvements in SLOTS, such as the step-and-stare method, the ceramic rod, and the Gaussian fitting processing software, so that this system supports higher accuracy and resolution. As a result, SLOTS is an optical testing system that covers a huge portion of the fabrication process from the grinding to the figuring. It is a complementary solution for other metrology systems such as the laser tracker, SCOTS, and null interferometry. SLOTS can reduce the manufacturing time by producing ground aspheres that have low errors of the surface figure when polishing begins.
- Published
- 2018
13. Chebyshev gradient polynomials for high resolution surface and wavefront reconstruction
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Chang Jin Oh, James H. Burge, Greg Smith, Dae Wook Kim, Maham Aftab, and Logan R. Graves
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Wavefront ,Chebyshev polynomials ,Polynomial ,Data processing ,Computer science ,Scalar (mathematics) ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Chebyshev filter ,Metrology ,010309 optics ,ComputingMethodologies_SYMBOLICANDALGEBRAICMANIPULATION ,0103 physical sciences ,Orthonormal basis ,0210 nano-technology ,Algorithm - Abstract
A new data processing method based on orthonormal rectangular gradient polynomials is introduced in this work. This methodology is capable of effectively reconstructing surfaces or wavefronts with data obtained from deflectometry systems, especially during fabrication and metrology of high resolution and freeform surfaces. First, we derived a complete and computationally efficient vector polynomial set, called G polynomials. These polynomials are obtained from gradients of Chebyshev polynomials of the first kind – a basis set with many qualities that are useful for modal fitting. In our approach both the scalar and vector polynomials, that are defined and manipulated easily, have a straightforward relationship due to which the polynomial coefficients of both sets are the same. This makes conversion between the two sets highly convenient. Another powerful attribute of this technique is the ability to quickly generate a very large number of polynomial terms, with high numerical efficiency. Since tens of thousands of polynomials can be generated, mid-to-high spatial frequencies of surfaces can be reconstructed from high-resolution metrology data. We will establish the strengths of our approach with examples involving simulations as well as real metrology data from the Daniel K. Inouye Solar Telescope (DKIST) primary mirror.
- Published
- 2018
14. Manufacture of primary mirror segments for the Giant Magellan Telescope
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Buell T. Jannuzi, Victor Gasho, K. Law, Adrian R. Loeff, M. T. Tuell, T. J. McMahon, S. N. Weinberger, J. S. Kingsley, Dae Wook Kim, R. D. Lutz, R. G. Allen, Hubert M. Martin, S. C. West, and Chang Jin Oh
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Primary mirror ,Giant Magellan Telescope ,Upgrade ,Optical testing ,Polishing ,Surface processing ,Geodesy ,Geology - Abstract
The Richard F. Caris Mirror Lab at the University of Arizona continues the production of 8.4 m lightweight honeycomb segments for the primary mirror of the Giant Magellan Telescope. GMT will have a center segment surrounded by six identical off-axis segments, plus an additional off-axis segment to allow continuous operation as segments are removed for coating. Production highlights of the last two years include the spin-casting of Segment 5, preliminary polishing of Segment 2, and completion of the rear surface processing for Segments 3 and 4. We completed a preliminary design of the significant modifications of the test systems required for Segment 4, the center segment. We finished an upgrade of the 8.4 m polishing machine; both the upgrade and experience gained with Segment 1 have contributed to much faster polishing convergence for Segment 2. Prior to polishing Segment 2, we verified the stability and accuracy of the measurement systems by re-measuring Segment 1, achieving good agreement among multiple independent tests as well as good agreement with the original acceptance tests of Segment 1.
- Published
- 2018
15. Measurement of large on-axis and off-axis mirrors using software configurable optical test system
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Chang Jin Oh, Steven C. West, Lori Harrison, Greg Smith, and Andrew E. Lowman
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Figuring ,business.industry ,Dynamic range ,Computer science ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Metrology ,law.invention ,010309 optics ,Telescope ,Interferometry ,Giant Magellan Telescope ,Software ,Optics ,law ,0103 physical sciences ,Calibration ,0210 nano-technology ,business - Abstract
One of the major challenges of optical fabrication is measurement of the surface when first polished out, before its figure is within the capture range of interferometry. A high dynamic range instrument with good accuracy is needed to efficiently guide the processing. Our approach is to use the Software Configurable Optical Test System (SCOTS), a deflectometry technique that uses a camera and liquid crystal display to measure the surface slope. We describe the use of SCOTS in the fabrication of a 6.5 m on-axis mirror and an 8.4 m off-axis mirror segment (Giant Magellan Telescope primary). SCOTS has the dynamic range to measure high slope errors early in the mirror figuring process, with sufficient accuracy to corroborate later interferometric measurements. Accurately measuring low order figure errors with SCOTS requires careful calibration of the system geometry. Details of the data collection and processing, and comparison to interferometry measurements are presented.
- Published
- 2018
16. Fabrication, integration and testing of 6.5m primary mirror and telescope cell assembly for the University of Tokyo Atacama Observatory (Conference Presentation)
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Greg Smith, Andrew E. Lowman, Matthew B. Dubin, Thomas Connors, William Verts, Chang Jin Oh, and Jamison Noenickx
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Telescope ,Primary mirror ,Interferometry ,Fabrication ,Integration testing ,law ,Computer science ,Optical engineering ,Mechanical engineering ,Polishing ,Metrology ,law.invention - Abstract
The Optical Engineering and Fabrication Facility (OEFF) at the College of Optical Sciences, University of Arizona has successfully fabricated a 6.5m primary mirror and conducted integration and testing (I & T) of the primary mirror and telescope cell assembly for the University of Tokyo Atacama Observatory. The mirror has been fabricated using a new facility and advanced technologies developed by the group, including fabrication process optimization, a super-stable optical metrology support, infrared and visible metrology with high accuracy, and interferometry. Fabrication process optimization has simulated the entire fabrication process from the initial grinding to final polishing to specification, and optimized the tooling, frequency of metrology, and estimated convergence. Through the project the new process optimization successfully demonstrated the performance and guided the process in a deterministic way. The 6.5m primary mirror is made of E6 bolo-silicate glass with a honeycomb structure. Due to the scale it requires a mechanically and thermally stable metrology support to ensure highly accurate metrology. The new metrology support has demonstrated its extremely stable force stability and thermal stability over the project period. Metrology of large optics is always a challenge and the OEFF group has made outstanding advancement in IR and visible metrology and applied them seamlessly during the mirror fabrication with extremely low uncertainty. By applying the newly developed facility and technologies, the OEFF group successfully fabricated the 6.5m primary mirror in less than 7months, which is about 3 times faster than past 6.5m mirror fabrication at UA. After fabrication the mirror was integrated to the telescope cell and the primary mirror cell assembly has been tested using optical metrology to identify the static and dynamic behavior of the system. The testing includes support actuator influence functions, the nominal support force set, bending mode correction, and assessment of deliverable image quality. This paper presents the technical aspects of the mirror fabrication, advancement of metrology and I & T of the 6.5m primary mirror assembly.
- Published
- 2018
17. Process optimization for efficient convergence in large optics fabrication
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Andrew E. Lowman, Chang Jin Oh, Greg Smith, and Hubert M. Martin
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Primary mirror ,Fabrication ,Computer science ,Optical engineering ,Electronic engineering ,Material removal ,Process optimization ,Secondary mirror ,Critical path method ,Metrology - Abstract
Large optic fabrication is a delicate and time consuming process. Obtaining a large prime optic is often in the critical path of a project and poses a serious risk to both the schedule and budget. The Optical Engineering and Fabrication Facility (OEFF) at the College of Optical Sciences, the University of Arizona, has developed a new way of optimizing its large optic fabrication process for maximum efficiency in convergence. The new process optimization takes the amount of stock material removal, tool characteristics, metrology uncertainty, optic prescription, optic material properties, and resource availability as input parameters and provides an optimized process along with an achievable convergence. This paper presents technical details of the new process optimization and demonstrates performance on 6.5m mirror fabrication at the University of Arizona. Two case studies for an 8.4m GMT off-axis primary mirror segment and a 3.1m TMT convex secondary mirror fabrication are also presented.
- Published
- 2018
18. An inexpensive turnkey 6.5-m observatory with customizing options
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J. S. Kingsley, Mario Rascon, Kerry L. Gonzales, Dae Wook Kim, Tom Connors, Chang Jin Oh, K. Peyton, Buell T. Jannuzi, Warren B. Davison, Jared R. Males, Hubert M. Martin, B. Assenmacher, Dan Alfred, Dennis Zaritsky, D. Neff, E. Christensen, J. Teran, P. M. Hinz, E. Pearce, R. Seaman, Roger Angel, and D. Adriaanse
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Telescope ,Primary mirror ,Engineering ,Focus (computing) ,law ,business.industry ,Observatory ,Ground layer ,Turnkey ,business ,Adaptive optics ,law.invention ,Remote sensing - Abstract
A turnkey observatory with 6.5-m telescope has been developed for a broad range of science applications. The observatory includes the telescope, mount and enclosure, installed on site and ready for operation. The telescope’s primary mirror is an f/1.25 honeycomb sandwich of borosilicate glass, similar to that of the MMT and Magellan telescopes. The baseline optical design is for a Gregorian Nasmyth focus at f/11. A Gregorian adaptive optics secondary that provides a wide-field focus corrected for ground layer turbulence (0.25 arcsecond images over a 4 arcminute field) as well as a narrow-field diffraction-limited focus is optional. Another option is a corrected f/5 focus with a 1° field. The observatory, built by partners from academia and industry with extensive experience, can be delivered within five years at a fixed price.
- Published
- 2018
19. Dynamic metrology and data processing for precision freeform optics fabrication and testing
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Chang Jin Oh, Isaac Trumper, Wenchuan Zhao, Dae Wook Kim, Lei Huang, Logan R. Graves, Heejoo Choi, and Maham Aftab
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Accuracy and precision ,Data processing ,Materials science ,Null (radio) ,business.industry ,Instantaneous phase ,Deformable mirror ,Metrology ,Interferometry ,Optics ,Computer vision ,Artificial intelligence ,business ,Gradient descent - Abstract
Dynamic metrology holds the key to overcoming several challenging limitations of conventional optical metrology, especially with regards to precision freeform optical elements. We present two dynamic metrology systems: 1) adaptive interferometric null testing; and 2) instantaneous phase shifting deflectometry, along with an overview of a gradient data processing and surface reconstruction technique. The adaptive null testing method, utilizing a deformable mirror, adopts a stochastic parallel gradient descent search algorithm in order to dynamically create a null testing condition for unknown freeform optics. The single-shot deflectometry system implemented on an iPhone uses a multiplexed display pattern to enable dynamic measurements of time-varying optical components or optics in vibration. Experimental data, measurement accuracy / precision, and data processing algorithms are discussed.
- Published
- 2017
20. Fabrication and Dynamic Deflectometry Testing Methods for Freeform and Deformable Optics
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Hyukmo Kang, S. C. West, J. S. Kingsley, Dae Wook Kim, Isaac Trumper, Greg Smith, Heejoo Choi, Logan R. Graves, Andrew E. Lowman, Maham Aftab, Hubert M. Martin, Chang Jin Oh, and M. T. Tuell
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Manufacturing technology ,Interferometry ,Engineering drawing ,Optics ,Fabrication ,Stochastic gradient descent ,Computer science ,business.industry ,Optical testing ,business ,Realization (systems) ,Design space ,Deformable mirror - Abstract
The diverse design space of freeform and deformable optics allows the design of innovative optical system concepts. A manufacturing technology is the remaining piece that prevents full realization of a freeform and adaptable optics age.
- Published
- 2017
21. Rectangular domain curl polynomial set for optical vector data processing and analysis
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Logan R. Graves, Maham Aftab, Greg Smith, Chang Jin Oh, Dae Wook Kim, and James H. Burge
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Curl (mathematics) ,Wavefront ,Polynomial ,Chebyshev polynomials ,Data processing ,Optical engineering ,Mathematical analysis ,Astrophysics::Instrumentation and Methods for Astrophysics ,General Engineering ,Orthonormal basis ,Atomic and Molecular Physics, and Optics ,Mathematics ,Metrology - Abstract
Rectangular pupils are employed in many optical applications such as lasers and anamorphic optics, as well as for detection and metrology systems such as some Shack−Hartmann wavefront sensors and deflectometry systems. For optical fabrication, testing, and analysis in the rectangular domain, it is important to have a well-defined set of polynomials that are orthonormal over a rectangular pupil. Since we often measure the gradient of a wavefront or surface, it is necessary to have a polynomial set that is orthogonal over a rectangular pupil in the vector domain as well. We derive curl (called C) polynomials based on two-dimensional (2-D) versions of Chebyshev polynomials of the first kind. Previous work derived a set of polynomials (called G polynomials) that are obtained from the gradients of the 2-D Chebyshev polynomials. We show how the two sets together can be used as a complete representation of any vector data in the rectangular domain. The curl polynomials themselves or the complete set of G and C polynomials has many interesting applications. Two of those applications shown are systematic error analysis and correction in deflectometry systems and mapping imaging distortion.
- Published
- 2019
22. Delivery, installation, on-sky verification of the Hobby Eberly Telescope wide field corrector
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Bryan Smith, Chang Jin Oh, Eric Frater, Matthew Shetrone, Herman Kriel, John M. Good, James H. Burge, Gary J. Hill, Hanshin Lee, Emily Schroeder, Brian L. Vattiat, and Jerry Martin
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Physics ,Field of view ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,010309 optics ,Telescope ,Upgrade ,Integral field spectrograph ,law ,Observatory ,Sidereal time ,0103 physical sciences ,Hobby–Eberly Telescope ,0210 nano-technology ,Spectrograph ,Remote sensing - Abstract
The Hobby-Eberly Telescope (HET)†, located in West Texas at the McDonald Observatory, operates with a fixed segmented primary (M1) and has a tracker, which moves the prime-focus corrector and instrument package to track the sidereal and non-sidereal motions of objects. We have completed a major multi-year upgrade of the HET that has substantially increased the pupil size to 10 meters and the field of view to 22 arcminutes by deploying the new Wide Field Corrector (WFC), new tracker system, and new Prime Focus Instrument Package (PFIP). The focus of this paper is on the delivery, installation, and on-sky verification of the WFC. We summarize the technical challenges encountered and resolutions to overcome such challenges during the construction of the system. We then detail the transportation from Tucson to the HET, on-site ground verification test results, post-installation static alignment among the WFC, PFIP, and M1, and on-sky verification of alignment and image quality via deploying multiple wavefront sensors across 22 arcminutes field of view. The new wide field HET will feed the revolutionary new integral field spectrograph called VIRUS, in support of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), a new low resolution spectrograph (LRS2), an upgraded high resolution spectrograph (HRS2), and later the Habitable Zone Planet Finder (HPF).
- Published
- 2016
23. Development of the fast steering secondary mirror assembly of GMT
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Chan Park, Andrew Rakich, Lee R. Dettmann, Ueejeong Jeong, Chris Alongi, Yang Noh Yoon, Byeong-Gon Park, Ho Soon Yang, Sungho Lee, Il Kwon Moon, Paul Gardner, Robert Bernier, Wylie Rosenthal, Chang Jin Oh, Ho-Sang Kim, Je Heon Song, Jeong Yeol Han, Christoph Dribusch, Myung Cho, Kyoung Don Lee, Won Hyun Park, and Youra Jun
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Computer science ,business.industry ,Aperture ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,010309 optics ,Telescope ,Giant Magellan Telescope ,law ,0103 physical sciences ,Extremely Large Telescope ,0210 nano-technology ,Secondary mirror ,business ,Simulation ,Computer hardware - Abstract
The Giant Magellan Telescope (GMT) will be featured with two Gregorian secondary mirrors, an adaptive secondary mirror (ASM) and a fast-steering secondary mirror (FSM). The FSM has an effective diameter of 3.2 m and built as seven 1.1 m diameter circular segments, which are conjugated 1:1 to the seven 8.4m segments of the primary. Each FSM segment contains a tip-tilt capability for fine co-alignment of the telescope sub-apertures and fast guiding to attenuate telescope wind shake and mount control jitter. This tip-tilt capability thus enhances performance of the telescope in the seeing limited observation mode. As the first stage of the FSM development, Phase 0 study was conducted to develop a program plan detailing the design and manufacturing process for the seven FSM segments. The FSM development plan has been matured through an internal review by the GMTO-KASI team in May 2016 and fully assessed by an external review in June 2016. In this paper, we present the technical aspects of the FSM development plan.
- Published
- 2016
24. Manufacturing of super-polished large aspheric/freeform optics
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Greg Smith, James H. Burge, Chang Jin Oh, Dae Wook Kim, Andrew E. Lowman, and Maham Aftab
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Physics ,business.industry ,Optical engineering ,Zerodur ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Solar telescope ,law.invention ,Metrology ,010309 optics ,Telescope ,Primary mirror ,Optics ,law ,0103 physical sciences ,Spatial frequency ,Bidirectional reflectance distribution function ,0210 nano-technology ,business - Abstract
Several next generation astronomical telescopes or large optical systems utilize aspheric/freeform optics for creating a segmented optical system. Multiple mirrors can be combined to form a larger optical surface or used as a single surface to avoid obscurations. In this paper, we demonstrate a specific case of the Daniel K. Inouye Solar Telescope (DKIST). This optic is a 4.2 m in diameter off-axis primary mirror using ZERODUR thin substrate, and has been successfully completed in the Optical Engineering and Fabrication Facility (OEFF) at the University of Arizona, in 2016. As the telescope looks at the brightest object in the sky, our own Sun, the primary mirror surface quality meets extreme specifications covering a wide range of spatial frequency errors. In manufacturing the DKIST mirror, metrology systems have been studied, developed and applied to measure low-to-mid-to-high spatial frequency surface shape information in the 4.2 m super-polished optical surface. In this paper, measurements from these systems are converted to Power Spectral Density (PSD) plots and combined in the spatial frequency domain. Results cover 5 orders of magnitude in spatial frequencies and meet or exceed specifications for this large aspheric mirror. Precision manufacturing of the super-polished DKIST mirror enables a new level of solar science.
- Published
- 2016
25. Modern technologies of fabrication and testing of large convex secondary mirrors
- Author
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Chunyu Zhao, Eric Frater, Greg Smith, Chang Jin Oh, James H. Burge, Andrew E. Lowman, and Matt Dubin
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Physics ,Fabrication ,Aperture ,business.industry ,02 engineering and technology ,Large Synoptic Survey Telescope ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,Metrology ,010309 optics ,Image stitching ,Telescope ,Interferometry ,Optics ,law ,0103 physical sciences ,0210 nano-technology ,business ,Secondary mirror - Abstract
Modern large telescopes such as TAO, LSST, TMT and EELT require 0.9m-4m monolithic convex secondary mirrors. The fabrication and testing of these large convex secondary mirrors of astronomical telescopes is getting challenging as the aperture of the mirror is getting bigger. The biggest challenge to fabricate these large convex aspheric mirrors is to measure the surface figure to a few nanometers, while maintaining the testing and fabrication cycle to be efficient to minimize the downtime. For the last a couple of decades there was huge advancement in the metrology and fabrication of large aspheric secondary mirrors. College of Optical Sciences in the University Arizona developed a full fabrication and metrology process with extremely high accuracy and efficiency for manufacturing the large convex secondary mirrors. In this paper modern metrology systems including Swing-Arm Optical Coordinate Measuring System (SOCMM) which is comparable to Interferometry and a Sub-aperture stitching interferometry scalable to a several meters have been presented. Also a Computer Controlled Fabrication Process which produces extremely fine surface figure and finish has been demonstrated. These most recent development has been applied to the fabrication and testing of 0.9m aspheric convex secondary mirror for the Tokyo Atacama Observatory’s 6.5m telescope and the result has been presented.
- Published
- 2016
26. Fabrication and testing of 4.2m off-axis aspheric primary mirror of Daniel K. Inouye Solar Telescope
- Author
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Greg Smith, James H. Burge, Run Huang, Ping Zhou, Peng Su, Daewook Kim, Chunyu Zhao, Andrew E. Lowman, Tianquan Su, and Chang Jin Oh
- Subjects
Physics ,Aperture ,business.industry ,Reflecting telescope ,Daniel K. Inouye Solar Telescope ,Astrophysics::Instrumentation and Methods for Astrophysics ,01 natural sciences ,Solar telescope ,Metrology ,law.invention ,010309 optics ,Primary mirror ,Telescope ,Interferometry ,Optics ,law ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,business ,010303 astronomy & astrophysics - Abstract
Daniel K. Inouye Solar Telescope (formerly known as Advanced Technology Solar Telescope) will be the largest optical solar telescope ever built to provide greatly improved image, spatial and spectral resolution and to collect sufficient light flux of Sun. To meet the requirements of the telescope the design adopted a 4m aperture off-axis parabolic primary mirror with challenging specifications of the surface quality including the surface figure, irregularity and BRDF. The mirror has been completed at the College of Optical Sciences in the University of Arizona and it meets every aspect of requirement with margin. In fact this mirror may be the smoothest large mirror ever made. This paper presents the detail fabrication process and metrology applied to the mirror from the grinding to finish, that include extremely stable hydraulic support, IR and Visible deflectometry, Interferometry and Computer Controlled fabrication process developed at the University of Arizona.
- Published
- 2016
27. Taraxerone enhances alcohol oxidation via increases of alcohol dehyderogenase (ADH) and acetaldehyde dehydrogenase (ALDH) activities and gene expressions
- Author
-
Seung-Mi Kim, Chang-Keun Sung, Sun-A Yang, Chang-Jin Oh, Eun-Kyoung Mo, and Byung-Hee Han
- Subjects
medicine.medical_specialty ,Aldehyde dehydrogenase ,Alcohol ,Toxicology ,Gene Expression Regulation, Enzymologic ,Mice ,chemistry.chemical_compound ,Internal medicine ,medicine ,Animals ,Oleanolic Acid ,Ethanol metabolism ,DNA Primers ,Alcohol dehydrogenase ,Ethanol ,Base Sequence ,biology ,Reverse Transcriptase Polymerase Chain Reaction ,Alcohol Dehydrogenase ,Acetaldehyde ,General Medicine ,Glutathione ,Aldehyde Oxidoreductases ,Endocrinology ,chemistry ,Biochemistry ,Catalase ,Alcohols ,biology.protein ,Oxidation-Reduction ,Food Science - Abstract
The present study, taraxerone (d-friedoolean-14-en-3-one) was isolated from Sedum sarmentosum with purity 96.383%, and its enhancing effects on alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH) activities were determined: EC(50) values were 512.42 ± 3.12 and 500.16 ± 3.23 μM for ADH and ALDH, respectively. In order to obtain more information on taraxerone related with the alcohol metabolism, 40% ethanol (5 mL/kg body weight) with 0.5-1mM of taraxerone were administered to mice. The plasma alcohol and acetaldehyde concentrations of taraxerone-treated groups were significantly lowered than those of the control group (p
- Published
- 2012
28. Characterization of Korean traditional medicine Chongmyungtang for cognitive function related to anti-cholinesterases and antioxidant activity
- Author
-
Beom Sik Yun, Mi Ra Lee, Byung Chan Kim, Chang Jin Oh, Hyun In Oh, and Chang Keun Sung
- Subjects
congenital, hereditary, and neonatal diseases and abnormalities ,food.ingredient ,Antioxidant ,Traditional medicine ,biology ,Chemistry ,Aché ,medicine.medical_treatment ,biology.organism_classification ,Applied Microbiology and Biotechnology ,language.human_language ,nervous system diseases ,food ,Acorus gramineus ,Herb ,Memory improvement ,Polygala tenuifolia ,medicine ,language ,IC50 ,Butyrylcholinesterase ,Food Science ,Biotechnology - Abstract
Chongmyungtang (CMT) is a traditional Korean herbal medicine, used therapeutically for memory improvement. It consists of 3 herbs, wongi (Polygala tenuifolia Willdenow, WNG), sukchangpo (Acorus gramineus Soland, SCP), and bokshin (Poria cocos Wolf, BKS). This study evaluated CMT and its components in terms of anti-cholinesterases (ChEs) activity, antioxidant activity, and their effects on memory in mice. CMT displayed the highest inhibition towards acetylcholinesterase (AChE), followed by WNG, SCP, and BKS. WNG was found to be the most effective herb with an estimated IC50 value of 0.94 mg/mL on butyrylcholinesterase (BuChE) inhibition. At a concentration of 5 mg/mL, DPPH scavenging activities of CMT, WNG, and SCP reached a plateau of about 90%. WNG exhibited the highest total phenolic contents followed by CMT, SCP, and BKS. CMT and its components prolonged the step-through latency shortened by scopolamine. These results suggest that CMT shows potential cognitive improvement by inhibition of ChEs and promotion of antioxidant activity.
- Published
- 2011
29. Assessment of antioxidant capacity of sedum (Sedum sarmentosum) as a valuable natural antioxidant source
- Author
-
Seung Mi Kim, Eun Kyoung Mo, Sun A Yang, Chang Keun Sung, and Chang Jin Oh
- Subjects
Antioxidant ,Oxygen radical absorbance capacity ,Chemistry ,DPPH ,medicine.medical_treatment ,Applied Microbiology and Biotechnology ,Ferric reducing ability of plasma ,chemistry.chemical_compound ,Biochemistry ,Polyphenol ,Sedum sarmentosum ,medicine ,TBARS ,Butylated hydroxytoluene ,Food science ,Food Science ,Biotechnology - Abstract
In order to investigate the antioxidant capacity of sedum (dolnamul, Sedum sarmentosum) and to offer a scientific basis for the medicinal use of it, lyophilized sedum leaves were extracted with n-hexane, n-butanol, ethyl acetate, and methanol, respectively. The methanol extract (ME) showed the highest extraction yield, but no significant differences in the extraction yield were observed. The total polyphenol content (TPC) of the ethyl acetate extract (EAE) and the ME was significantly higher than that of the non-polar solvent extracts. The EAE and ME showed the superior antioxidant activities in the DPPH, oxygen radical absorbance capacity (ORAC), and ferric reducing ability of plasma (FRAP) assays. Lipid peroxidation was efficiently inhibited by the addition of the sedum extracts in the ferric thiocyanate (FTC) and thiobarbituric acid reactive substances (TBARS) assays, but significant differences among the tested extracts were not observed. The ME showed the potent lipid peroxidation inhibitory activity comparable to butylated hydroxytoluene (BHT). The correlations between the TPC and the antioxidant activities based on the DPPH, ORAC, and FRAP assays were highly positive (R 2>0.899).
- Published
- 2011
30. Evaluation of the Oral Acute Toxicity of Black Ginseng in Rats
- Author
-
Zheng Li, Chang-Jin Oh, Chun-Yan Wang, Beong Ou Lim, Sang-Hwa Lee, Li-Juan Gu, Jae-Il Lee, Zhen Wang, Mi-Ra Lee, Jing-Jie Li, and Chang-Keun Sung
- Subjects
Single administration ,business.industry ,medicine.medical_treatment ,Pharmacology ,Body weight ,Biochemistry, Genetics and Molecular Biology (miscellaneous) ,Acute toxicity ,Ginseng ,chemistry.chemical_compound ,Complementary and alternative medicine ,chemistry ,Oral administration ,Toxicity ,Urea ,Medicine ,business ,Saline ,Biotechnology - Abstract
We studied the acute oral toxicity of black ginseng (BG) produced by heat process in rats. Single acute BG extract doses of 0, 5, 10, and 15 g/㎏ dissolved in saline were administered by oral gavage and the animals were kept under observation for 14 days. The single administration of BG extract up to 15 g/㎏ did not produce mortality, behavioral change or abnormal clinical signs in the rats. These results indicated that the oral LD?? of the BG extract in the rats is higher than 15 g/㎏. Compared to the control group, no treatment-related biologically signifi cant effects of BG extract were noted in the measurements of the body weight or food intake. At the end of the period, the biochemical parameters and hematological parameters were analyzed in the plasma and blood. A histopathological examination of the liver and kidney was also conducted. Only the blood nitrogen urea and potassium levels in the biochemical indices showed signifi cant differences at 10 and 15 g/㎏ doses of BG extract compared to the control group. These changes were not considered to be due to the toxicity. None of the other clinical chemistry parameters were affected. Therefore, these results indicate that the BG by heat processing is virtually nontoxic.
- Published
- 2011
31. Characterization of Black Ginseng Extract with Acetyl- and Butyrylcholinesterase Inhibitory and Antioxidant Activities
- Author
-
Eun Kyung Mo, Mi Ra Lee, Jeong Hee Cho, Li Juan Gu, Beom Sik Yun, Chang Jin Oh, Chun-Yan Wang, and Chang Keun Sung
- Subjects
chemistry.chemical_classification ,Antioxidant ,biology ,Traditional medicine ,medicine.medical_treatment ,Saponin ,food and beverages ,complex mixtures ,Biochemistry, Genetics and Molecular Biology (miscellaneous) ,Acetylcholinesterase ,Superoxide dismutase ,chemistry.chemical_compound ,Ginseng ,Complementary and alternative medicine ,chemistry ,Ginsenoside ,medicine ,biology.protein ,Xanthine oxidase ,Butyrylcholinesterase ,Biotechnology - Abstract
Black ginseng and white ginseng were extracted with 80% ethanol and evaluated for relative ginsenoside composition, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities, and antioxidant properties. As analyzed by HPLC, black ginseng contained a greater proportion of ginsenoside Rg₃ compared to white ginseng. White ginseng was characterized by undetectable ginsenoside Rg₃ but it contained more total ginsenosides than black ginseng. Black ginseng extract exhibited higher (p<0.05) free radical-scavenging activity, as well as higher antioxidant activities than white ginseng against 2,2-diphenyl-1-picryl-hydrazyl, superoxide dismutase, and xanthine oxidase, despite the fact that the total saponin content was higher in white ginseng than black ginseng. In addition, the black ginseng extract displayed greater AChE and BChE inhibitory activities. These results suggest that black ginseng has stronger effects on anti-oxidation and AChE and BChE inhibition than white ginseng.
- Published
- 2010
32. Positive-/Negative-, Erasable-/Immobilized-, Mono-/Multi-Color Fluorescence Image Patterning of Molecular-Scale Porous Polymer Film via a Microcontact Printing Method Using Various Chemical Inks
- Author
-
Heejun Jeong, Giseop Kwak, Wang-Eun Lee, Chang-Jin Oh, Keun-Byoung Yoon, and Hyo-Sang Park
- Subjects
chemistry.chemical_classification ,Materials science ,Quenching (fluorescence) ,Polymers and Plastics ,Inkwell ,Organic Chemistry ,Intermolecular force ,Polymer ,Fluorescence ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Acetylene ,Microcontact printing ,Polymer chemistry ,Materials Chemistry ,Porosity - Abstract
Fluorescent image patterns of a substituted acetylene polymer film with a large FFV were successfully obtained by a µCP method using several kinds of chemical ink compounds. PO and SCA generated positive-type fluorescent image patterns. On the other hand, an ethanolic solution of DNT generated a negative-type fluorescent image pattern due to a significant quenching effect. An NMP solution of NR gave a two-color image pattern due to an intermolecular energy transfer from PTMSDPA to NR.
- Published
- 2010
33. Preparation and Thermal Properties of Aliphatic Network Polyester-Silica Composites
- Author
-
Dong Cheul Han, Chang Jin Oh, Su Dong Park, and Gi Seop Kwak
- Subjects
chemistry.chemical_classification ,Materials science ,Polymers and Plastics ,General Chemical Engineering ,Composite number ,Polymer ,Thermal treatment ,engineering.material ,Polyester ,Thermal conductivity ,chemistry ,Coating ,Thermoelectric effect ,Materials Chemistry ,engineering ,Knoevenagel condensation ,Composite material - Abstract
The hybrid composites of aliphatic polyester-silica were prepared via a sol-gel reaction and their potential application using as a buffer coating layer in the thermoelectric device were investigated. When aliphatic polyesters were thermally treated at a high temperature of 240 ℃, the polymer showed an increases in thermal degradation temperature by 30∼90 ℃ according to the thermal treatment time. The polyester-silica composites showed an increases in thermal degradation temperature by 30∼50 ℃ according to the content of the added silica. Polyester-silica composite showed neither discoloration nor change in optical properties because Knoevenagel condensation reaction was hindered by silica structure. The thermal conductivity of the composites increased linearly according to the content of added silica.
- Published
- 2010
34. Diphenylacetylene Polymer Nanofiber Mats Fabricated by Freeze Drying: Preparation and Application for Explosive Sensors
- Author
-
Giseop Kwak, Inn-Kyu Kang, Wang-Eun Lee, and Chang-Jin Oh
- Subjects
chemistry.chemical_classification ,Materials science ,Quenching (fluorescence) ,Polymers and Plastics ,Chemical structure ,Organic Chemistry ,Polymer ,Condensed Matter Physics ,Freeze-drying ,chemistry.chemical_compound ,chemistry ,Nanofiber ,Polymer chemistry ,Materials Chemistry ,Gas detector ,Physical and Theoretical Chemistry ,Thin film ,Diphenylacetylene - Abstract
Finely structured diphenylacetylene polymer nanofibers were successfully prepared by a freeze drying method. SEM revealed that the morphology and structure of the fibers were significantly dependent on the concentration of the polymer solution, the 'frozen in' quenching temperature and the chemical structure of the polymer derivatives. Polarized fluorescence spectroscopy revealed that the polymer chains within the nanofiber were uniaxially oriented and highly elongated. The polymer nanofiber was remarkably sensitive to explosive nitroaromatic compounds when compared to the corresponding thin films. The fluorescence of polymer nanofiber obtained from 0.003 wt.-% cryogenic benzene solution rapidly decreased to 50% of its initial value in ≈35 s by exposing to 2,4-dinitrotoluene.
- Published
- 2010
35. Extremely large freeform optics manufacturing and testing
- Author
-
James H. Burge, Peng Su, Chang Jin Oh, and Dae Wook Kim
- Subjects
Physics ,Primary mirror ,Optical imaging ,Optics ,Optical diffraction ,Etendue ,business.industry ,Infrared ,Stray light ,Optoelectronics ,Active optics ,business ,Solar telescope - Abstract
The 4.2m Daniel K. Inouye Solar Telescope (DKIST) primary mirror has about 9 mm freeform aspheric departure. Actively controlled stressed lap and infrared deflectometry system have been developed to manufacture the extremely large freeform optics.
- Published
- 2015
36. Accurate and rapid IR metrology for the manufacture of freeform optics
- Author
-
Dae Wook Kim, Tianquan Su, Peng Su, Chang-jin Oh, Logan Graves, and James Burge
- Published
- 2015
37. Measurement of large on-axis and off-axis mirrors using Software Configurable Optical Test System (SCOTS).
- Author
-
Lowman, Andrew E., Smith, Greg A., Harrison, Lori, West, Steven C., and Chang Jin Oh
- Published
- 2018
- Full Text
- View/download PDF
38. Process optimization for efficient convergence in large optics fabrication.
- Author
-
Chang Jin Oh, Lowman, Andrew E., Martin, Hubert M., and Smith, Greg A.
- Published
- 2018
- Full Text
- View/download PDF
39. A swing arm method for profile measurement of large optical concave surfaces in the lapping process
- Author
-
Eung Suk Lee, In Kyoung Sung, Ock Hyun Kim, and Chang Jin Oh
- Subjects
Figuring ,Engineering ,business.industry ,Mechanical Engineering ,Process (computing) ,Curved mirror ,Mechanical engineering ,Polishing ,Swing ,Residual ,Industrial and Manufacturing Engineering ,Computer Science Applications ,Grinding ,Optics ,Lapping ,Control and Systems Engineering ,business ,Software - Abstract
Generally, optical components are fabricated by grinding, lapping, and polishing. Usually, these processes take a long time to obtain high surface quality. Therefore, in the case of large optical components, on-machine inspection (OMI) is essential, because the workpiece is fragile and difficult to set up for fabricating and measuring. This paper describes a swing arm method for measuring the surface profile of large optical concave mirrors. The measuring accuracy and uncertainty for the method are studied. Experimental results show that this method is especially useful in the lapping process, where an accuracy of 3–5 μm is obtained. Inspection data is also provided to correct the residual figuring error in lapping or polishing processes .
- Published
- 2006
40. A swing-arm on-machine inspection method for profile measurement of large optical surface in lapping process
- Author
-
Eung Suk Lee, Chang Jin Oh, In Kyoung Sung, and Ock Hyun Kim
- Subjects
Figuring ,Engineering ,business.industry ,Mechanical Engineering ,Mechanical engineering ,Polishing ,Coordinate-measuring machine ,Grinding ,Optics ,Lapping ,Machining ,Mechanics of Materials ,Surface metrology ,Profilometer ,business - Abstract
Generally, the optical components are fabricated by grinding, lapping, and polishing. And, those processes take long time to obtain such a high surface quality. Therefore, in the case of large optical component, the on-machine inspection (OMI) is essential. Because, the work piece is fragile and difficult to set up for fabricating and measuring. This paper is concerned about a swing-arm method for measuring surface profile of large optical concave mirror. The measuring accuracy and uncertainty for suggested method are studied. The experimental results show that this method is useful specially in lapping process with the accuracy of 3-5㎛. Those inspection data are provided for correcting the residual figuring error in lapping or polishing processes.
- Published
- 2005
41. Machining Accuracy for Large Optical Mirror using On-Machine Spherical Surface ]Referenced Shack-Hartmann System
- Author
-
Chang Jin Oh, Jong Hui Hong, Eung Suk Lee, and Ock Hyn Kim
- Subjects
Surface (mathematics) ,Engineering ,Optics ,Machining ,business.industry ,Mechanical Engineering ,business - Published
- 2005
42. A study on enhancement of grinding accuracy by an active tool control
- Author
-
Ock Hyun Kim and Chang Jin Oh
- Subjects
Engineering ,business.industry ,Mechanical Engineering ,Diamond ,PID controller ,engineering.material ,Optimal control ,Grinding ,Machining ,Control theory ,Control system ,business ,Diamond tool ,Machine control - Abstract
An approach to enhance dimensional accuracy of the grinding process has been presented, and grinding of a glass material with a metal-bonded diamond wheel has been studied. In this study, a grinding tool is suspended flexibly and controlled by an electromagnetic actuator. During grinding, profile error of a ground surface is indirectly measured and fed back to a control system. A model of grinding error has been suggested on which the indirect measurement has been based. An optimal PID control is adopted and effectiveness of the in-process feedback control has been verified experimentally.
- Published
- 2002
43. Development of a wide field spherical aberration corrector for the Hobby Eberly Telescope: design, fabrication and alignment
- Author
-
Andrew E. Lowman, Peng Su, Chang Jin Oh, James H. Burge, Eric Frater, Chunyu Zhao, and Ping Zhou
- Subjects
Point spread function ,Physics ,Fabrication ,business.industry ,Aperture ,law.invention ,Primary mirror ,Telescope ,Spherical aberration ,Optics ,law ,Hobby–Eberly Telescope ,business ,Focus (optics) - Abstract
A 4-mirror prime focus corrector is under development to provide seeing-limited images for the 10-m aperture Hobby- Eberly Telescope (HET) over a 22 arcminute wide field of view. The images created by the spherical primary mirror are aberrated with 13 arcmin diameter point spread function. The University of Arizona is developing the 4-mirror wide field corrector to compensate the aberrations from the primary mirror and present seeing limited imaged to the pickoffs for the fiber-fed spectrographs. The requirements for this system pose several challenges, including optical fabrication of the aspheric mirrors, system alignment, and operational mechanical stability. This paper presents current status of the program which covers fabrication of mirrors and structures and pretest result from the alignment of the system.
- Published
- 2014
44. Advanced Technology Solar Telescope 4.2 m Off-axis Primary Mirror Fabrication
- Author
-
James H. Burge, Dae Wook Kim, Peng Su, and Chang Jin Oh
- Subjects
Primary mirror ,Engineering ,Optics ,Fabrication ,business.industry ,Manufacturing process ,Stray light ,Optoelectronics ,Spatial frequency ,business ,Adaptive optics ,Solar telescope - Abstract
Advanced optical surfacing technologies are applied for the Advanced Technology Solar Telescope 4.2 m off-axis primary mirror fabrication. A newly developed Stressed lap and IR deflectometry system are demonstrated for a highly deterministic manufacturing process.
- Published
- 2014
45. Substitution position effect on photoluminescence emission and chain conformation of poly(diphenylacetylene) derivatives
- Author
-
Heung-Jin Choi, Michiya Fujiki, Guen-Tae Park, Wang-Eun Lee, Jin-Woo Kim, Ken-ichi Shinohara, Giseop Kwak, Toshikazu Sakaguchi, Ayako Nakao, and Chang-Jin Oh
- Subjects
Photoluminescence ,Substitution (logic) ,Metals and Alloys ,General Chemistry ,Photochemistry ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,Position effect ,Chain (algebraic topology) ,chemistry ,Intramolecular force ,Materials Chemistry ,Ceramics and Composites ,Diphenylacetylene - Abstract
The significant variation in photoluminescence emission of poly(diphenylacetylene) derivatives according to the substitution position is due to the differences in the intramolecular pi-stack structure and chain conformation.
- Published
- 2010
46. Alignment of four-mirror wide field corrector for the Hobby-Eberly Telescope
- Author
-
Andrew E. Lowman, Chang Jin Oh, Eric Frater, Laura E. Coyle, James H. Burge, Matt Dubin, and Chunyu Zhao
- Subjects
Computer science ,business.industry ,Fixture ,Laser ,Retroreflector ,law.invention ,Primary mirror ,Optical axis ,Telescope ,Tilt (optics) ,Optics ,Laser tracker ,law ,Hobby–Eberly Telescope ,business - Abstract
The Hobby-Eberly Telescope (HET) Wide Field Corrector (WFC) is a four-mirror optical system which corrects for aberrations from the 10-m segmented spherical primary mirror. The WFC mirror alignments must meet particularly tight tolerances for the system to meet performance requirements. The system uses 1-m class highly aspheric mirrors, which precludes conventional alignment methods. For the WFC system alignment a “center reference fixture” has been used as the reference for each mirror’s vertex and optical axis. The center reference fixtures have both a CGH and sphere mounted retroreflector (SMR) nests. The CGH is aligned to the mirror’s optical axis to provide a reference for mirror decenter and tilt. The vertex of each mirror is registered to the SMR nests on the center reference fixtures using a laser tracker. The spacing between the mirror vertices is measured during the system alignment using these SMR nest locations to determine the vertex locations. In this paper we present the procedures and results from creating and characterizing these center reference fixtures. As a verification of our alignment methods we also present results from their application in the WFC system alignment are also presented.
- Published
- 2013
47. Algorithms for surface reconstruction from curvature data for freeform aspherics
- Author
-
Byoung Chang Kim, Dae Wook Kim, Chunyu Zhao, James H. Burge, and Chang Jin Oh
- Subjects
Surface (mathematics) ,Computer science ,Zernike polynomials ,Noise (signal processing) ,business.industry ,Curvature ,symbols.namesake ,Modal ,Signal-to-noise ratio ,symbols ,Computer vision ,Artificial intelligence ,Sensitivity (control systems) ,business ,Algorithm ,Surface reconstruction - Abstract
Increasing demand for highly accurate freeform aspheric surfaces requires accurate and efficient measurement techniques. One promising possibility uses a sub-aperture scanning system that measures local curvature variations across the part. In this paper, we develop and demonstrate two different data processing algorithms, a zonal approach using Southwell integration method and a modal approach leveraging Zernike curvature basis, that reconstruct the surface 3-dimensional profiles from the curvature data. The performance of suggested methods and the sensitivity to noise is diagnosed for various SNR (Signal-to-Noise Ratio) cases.
- Published
- 2013
48. Optical testing for meter size aspheric optics
- Author
-
James H. Burge, Peng Su, Chunyu Zhao, and Chang Jin Oh
- Subjects
Computer science ,business.industry ,Optical engineering ,Holography ,Ranging ,Laser ,Computer-generated holography ,law.invention ,Interferometry ,Optics ,Laser tracker ,law ,Optical test ,business - Abstract
Several meter size steep aspheric optics, with aspheric departure ranging from 100μm to 2mm, have been successfully fabricated at the College of Optical Sciences at University of Arizona. Optical metrology systems have been developed for measuring the optical surfaces efficiently and accurately. These systems include laser tracker surface profiler, swing arm optical CMM with different type of sensors, slope measurements with SCOTS, the Software Configurable Optical Test System (SCOTS) and interferometry with computer generated holograms. We summarize the test methods and provide comparison of the relative strengths and weaknesses.
- Published
- 2012
49. Swing arm optical CMM: self calibration with dual probe shear test
- Author
-
Yuhao Wang, Peng Su, Chang Jin Oh, James H. Burge, and Robert E. Parks
- Subjects
Materials science ,Bearing (mechanical) ,Aperture ,business.industry ,Astrophysics::Instrumentation and Methods for Astrophysics ,Swing ,Signal ,law.invention ,Interferometry ,Air bearing ,Optics ,law ,Calibration ,Profilometer ,business - Abstract
Swing arm optical CMM (SOC), a profilometer with distance measuring interferometric probe for in situ measurement of the topography of aspheric has been used for measuring highly aspheric mirrors with a performance rivaling full aperture interferometric tests. Recently, we implemented a dual probe self calibration mode for the SOC. Data from the dual probes can be used to calibrate the swing-arm air bearing errors since both probes see the same bearing errors while measuring different portions of the test surface. Bearing errors are reconstructed from the shear signal with a modal estimation.
- Published
- 2011
50. Positive-/negative-, erasable-/immobilized-, mono-/multi-color fluorescence image patterning of molecular-scale porous polymer film via a microcontact printing method using various chemical inks
- Author
-
Hyosang, Park, Heejun, Jeong, Wang-Eun, Lee, Keun-Byoung, Yoon, Chang-Jin, Oh, and Giseop, Kwak
- Subjects
Molecular Imprinting ,Microscopy, Fluorescence ,Molecular Structure ,Polymers ,Color ,Ink ,Porosity ,Fluorescence - Abstract
Fluorescent image patterns of a substituted acetylene polymer film with a large FFV were successfully obtained by a µCP method using several kinds of chemical ink compounds. PO and SCA generated positive-type fluorescent image patterns. On the other hand, an ethanolic solution of DNT generated a negative-type fluorescent image pattern due to a significant quenching effect. An NMP solution of NR gave a two-color image pattern due to an intermolecular energy transfer from PTMSDPA to NR.
- Published
- 2010
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