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Optimization and Tolerance Scheme for a Mirror Mount Design Based on Optomechanical Performance
Hagyong Kihm,이윤우 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.3
We present the design optimization and tolerance scheme for the fold mirror system in our satellite telescope. A new type of mirror and mount flexure is proposed. The mirror is light-weight and is designed with an asymmetric off-axis configuration. The mount is a combination of monolithic axial and lateral supports. The design parameters of the flexure mount are optimized for optomechanical performances by using a simulated annealing method. The sensitivities of the optomechanical performances to the design parameters are tabulated to obtain tolerance for the critical dimensions by using finite element analysis (FEA). Optical distortions are examined with Zernike polynomials for qualitative analysis and design feedback. This unprecedented mirror and mount design would be a promising candidate for an asymmetric or off-axis optical system.
Athermal Elastomeric Lens Mount for Space Optics
Hagyong Kihm,양호순,문일권,Yun-Woo Lee 한국광학회 2009 Current Optics and Photonics Vol.13 No.2
We investigated the optimum adhesive thickness for athermalizing an elastomeric lens mount in our space optics application. Theoretical results were compared with finite element solutions using two different models; discrete circular pads and discrete circular pads with columns filling the insertion holes reflecting the reality. A noticeable difference between their optimal thicknesses was observed, and physical interpretation revealed the uncertainty of prevailing athermal equations. A pilot sample was made to check our results and thermo-optical stress was assessed using an interferometer after isothermal load. This study presented insight into preliminary design guidance in elastomeric lens mounting.
Bipod flexure for 1-m primary mirror system.
Kihm, Hagyong,Yang, Ho-Soon,Lee, Yun-Woo American Institute of Physics 2014 Review of scientific instruments Vol.85 No.12
<P>We present an analytical formulation of the bipod flexure for mounting the 1-m primary mirror in a space telescope. Compliance and stiffness matrices of the bipod flexure are derived to estimate theoretical performance and to make initial design guidelines. We use finite element analysis to optimize the bipod design satisfying the application requirements. Experimental verification is achieved by vibration test with a dummy mirror system.</P>
Adjustable bipod flexures for mounting mirrors in a space telescope
Kihm, Hagyong,Yang, Ho-Soon,Moon, Il Kweon,Yeon, Jeong-Heum,Lee, Seung-Hoon,Lee, Yun-Woo The Optical Society 2012 Applied Optics Vol.51 No.32
<P>A new mirror mounting technique applicable to the primary mirror in a space telescope is presented. This mounting technique replaces conventional bipod flexures with flexures having mechanical shims so that adjustments can be made to counter the effects of gravitational distortion of the mirror surface while being tested in the horizontal position. Astigmatic aberration due to the gravitational changes is effectively reduced by adjusting the shim thickness, and the relation between the astigmatism and the shim thickness is investigated. We tested the mirror interferometrically at the center of curvature using a null lens. Then we repeated the test after rotating the mirror about its optical axis by 180 in the horizontal setup, and searched for the minimum system error. With the proposed flexure mount, the gravitational stress at the adhesive coupling between the mirror and the mount is reduced by half that of a conventional bipod flexure for better mechanical safety under launch loads. Analytical results using finite element methods are compared with experimental results from the optical interferometer. Vibration tests verified the mechanical safety and optical stability, and qualified their use in space applications.</P>
Double-pass point diffraction interferometer
Kihm, Hagyong,Lee, Yun-Woo IOP Pub 2010 Measurement Science and Technology Vol.21 No.10
<P>We propose a new point diffraction interferometer for qualitative optical analysis. Point diffraction is made two times to generate interfering waves with a single pinholed polarizer. Diffraction from a pinholed polarizer makes reference and measurement waves with a double-pass configuration. A quarter-wave plate rotates their polarization angles after reciprocation. The interferogram between the diffracted–undiffracted measurement wave and the undiffracted–diffracted reference wave is vibration-insensitive due to a common-path configuration. We examined its capability by changing the pinhole size and divergence angle of the diffracted wave for test optics with various numerical apertures.</P>
Development of the primary mirror for CAS500-1 (Compact Advanced Satellite 500-1)
Kihm Hagyong,Lee Yun-Woo,Yang Ho-Soon,Kim Seonghui,Lee Deog-Gyu 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.6
CAS500-1 (Compact Advanced Satellite 500-1) launched in Mar. 2021 is the first Korean ground observation satellite localizing the entire mirror development, especially the primary mirror M1. M1 is a lightweight concave mirror with a diameter of 0.6 m, and it has 3 square bosses at the rim for flexure mounting. We present the whole development procedure of the flight model M1, including the optomechanical design, fabrication, environmental tests, and a coordinate mapping method for alignment and integration.
Fiber-diffraction interferometer for vibration desensitization.
Kihm, Hagyong,Kim, Seung-Woo Optical Society of America 2005 Optics letters Vol.30 No.16
<P>We describe a new interferometer designed to obtain high immunity to vibration by generating the reference wave by means of fiber diffraction so as to share a common path with the measurement wave. A spatial phase shifter is added to secure vibration desensitization by capturing four phase-shifted interferograms simultaneously without time delay. Experimental results prove that the proposed interferometer is capable of providing stable measurements with a level of fringe stabilization of less than 1 nm in a typical workshop environment equipped with no excessive ground isolation for antivibration.</P>
Athermal Lens Mount with Ring Flexures
Hagyong Kihm,양호순,Yun Woo Lee 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.6
We present a new athermal lens mounting scheme made of cascaded ring flexures. Two circular grooves are concentric at the adhesive injection hole and are fabricated monolithically on the lens cell or the barrel itself. The ring flexure can accommodate six-degree-of-freedom motions by controlling dimensional parameters. We evaluate thermo-elastic deformations by using interferometric measurements and verify the results with finite element analyses. Also, we compare the athermal performances from a simple elastomeric mount and a ring-flexured mount. This lens mounting scheme should be a promising candidate for environmentally-challenging optical systems like those used in space and military applications.