• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.57.3-58
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• 2016

We analyze an optical system of a telescope based on Fresnel type objective lens as suggested by Hyde (1999). The Fresnel objective lens can be thin, light-weight and foldable, and therefore it is possible to develop a space telescope with an aperture larger than that of traditional telescopes. Moreover a lens, whatever it is either Fresnel type or conventional, allows much larger fabrication tolerances. We design a medium-sized telescope adopting Fresnel lens as an objective lens for use in space and possibly on the ground. The well-known chromatic aberration of the Fresnel primary lens is corrected by a field lens and another Fresnel lens using Schupmann method. An additional lens is used for forming images. We analyze the chromatic and off-axis aberrations of the proposed system analytically and suggest methods for the minimization of off-axis aberrations and for the operation in wider spectral range. We also conduct ray tracing and optimize the whole optical system with commercial software. Finally we present the design parameters of a telescope with an aperture of 0.5 to 1 meters, enabling diffraction limited operation for a moderate field of view about 10 arc-minutes.

• Journal of Space Technology and Applications
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• v.1 no.1
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• pp.104-120
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• 2021

Some optical schemes of lenses for spacecraft developed by the author are considered. The main optical characteristics of telescope lenses of various architectures are compared. We propose compact solutions of mirror, lens-mirror, and lens systems with maximum available angular resolutions and other parameters. Examples of calculating the optical systems of lenses used for various tasks both in the field of astronomy and in the field of remote sensing of the Earth and other planets are given. The example of onboard computer system is discussed. Practical recommendations on the development and use of telescope lenses are given.

• Proceedings of the KIEE Conference
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• 2005.05a
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• pp.284-296
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• 2005

Bridge displacement measurement system using image processing is developed to overcome the contact type system inefficiencies such as heavy, expensive property and temporary construction necessity. The system is composed of tablet PC with IEEE1394 digital camera, telescope lens and a designed target mark. The key is projection algorithm where all pixels are added up for each row(column) to find out the center line. The experimental results are shown compared with a contact type system.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.36.2-36.2
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• 2010

The CQUEAN (Camera for QUasars in EArly uNiverse) is an optical CCD camera optimized for observation of high redshift objects. It is going to be attached to the cassegrain focus of 2.1m telescope at McDonald Observatory, USA. We are making a focal reducer for CQUEAN to secure a larger field of view. The focal reducer is composed of four spherical lens, and it reduces the focal length of telescope by one third. We designed the lens configuration, performed tolerance analysis, and estimated the optical performance with ZEMAX. The differences in optical performace with/without filters were also investigated. The result from ZEMAX shows that the system has ample margin of errors for median seeing of 1.2" at McDonald observatory. Even with aberration and alignment tolerance, the performance is better than the original requirement. The lenses are now being made, and the lens barrel and an adapter for assembly of the Andor CCD camera and the filter wheel is now under designing process. We expect that the manufacturing of the focal reducer system as well as its optical test will be finished by April 2010.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.389-392
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• 2015

We identify a strong lensing galaxy in the cluster IRC 0218 that is spectroscopically confirmed to be at z = 1.62, making it the highest-redshift strong lens galaxy known. The lens is one of the two brightest cluster galaxies and lenses a background source galaxy into an arc and a counterimage. With Hubble Space Telescope (HST) grism and Keck/LRIS spectroscopy, we measure the source redshift to be $z_S=2.26$. Using HST imaging, we model the lens mass distribution with an elliptical power-law profile and account for the effects of the cluster halo and nearby galaxies. The Einstein radius is $^{\theta}E=0.38^{+0.02{\prime}{\prime}}_{-0.01}$ ($3.2^{+0.2}_{-0.1}kpc$) and the total enclosed mass is $M_{tot}(<^{\theta}_E)=1.8^{+0.2}_{-0.1}{\times}10^{11}M_{\odot}$. We estimate that the cluster environment contributes ~ 10% of this total mass. Assuming a Chabrier IMF, the dark matter fraction within $^{\theta}E$ is $f^{Chab}_{DM}=0.3^{+0.1}_{-0.3}$, while a Salpeter IMF is marginally inconsistent with the enclosed mass ($f^{Salp}_{DM}=-0.3^{+0.2}_{-0.5}$).

• Korean Journal of Optics and Photonics
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• v.7 no.3
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• pp.183-190
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• 1996

To design three-mirror telescope system (F/8, 120 inch in focal length) for visible and infra-red band imaging, methods for power configuring and correction of the third order aberrations were studied. In the design of the telescope system, a three-mirror system corrected for spherical aberration, coma, and astigmatism was used for infra-red imaging, and the aberrations were corrected by using conic surfaces. For visible imaging, a singlet corrector lens was appended at the front of the focal plane to correct filed curvature. The telescope system has diffraction limited performance for 10 ${\mu}{\textrm}{m}$ in wavelength within 2.4$^{\circ}$ of field-of-view. In the visible band imaging, the rms spot size of the telescope system is less than 25 ${\mu}{\textrm}{m}$ within 3$^{\circ}$ of field-of-view for monochromatic light, and the telescope system satisfies flat field condition for CCD application.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.213-216
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• 2005

A novel hyperspectral imaging spectrometer controlling spatial and spectral resolution individually has been proposed. This imaging spectrometer uses a zoom lens as a telescope and a focusing element. It can change the spatial resolution fixing the spectral resolution or the spectral resolution fixing the spatial resolution. Here, we report the concept of the hyperspectral imaging spectrometer with the novel zooming function and the optical design of a zoom lens as the focusing element. By using lens module and third-order aberration theory, we have presented the initial design of four-group zoom lens with external entrance pupil. And the optimized zoom lens with a focal length of 50 to 150 mm is obtained from the initial design by the optical design software. As a result, the designed zoom lens shows satisfactory performances in wavelength range of 450 to 900 nm as a focusing element in an imaging spectrometer. Furthermore, the collimator lens of the imaging spectrometer is designed through the third-order aberration correction by using an iterative process.

• Journal of the Korean earth science society
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• v.30 no.7
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• pp.855-868
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• 2009

The purpose of this study was to investigate how teachers understand the principle of image formation of stars through a telescope. This study was conducted by using explanatory paper questionnaires given to 101 earth science teachers in the areas of Gyunggi province and Seoul. The questionnaires were cross-analyzed by three experts in earth science education. Result indicated that most of the participating teachers did not have systematic concepts about the process of making an image formed by a convex lens. Particulary, they did not sufficiently understand the concepts of an image and the functions of a screen. Furthermore, only 3% of the participants possessed the scientific concepts about the image formation principle of a star through the telescope. Most of the teachers seem to have non-scientific or alternative concepts about the image formation, which was only understanded with the fragmented characteristics about light and convex lens.

• Publications of The Korean Astronomical Society
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• v.22 no.4
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• pp.201-209
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• 2007

We have preliminarily designed two infrared optical systems of the multi-purpose infrared camera system (MIRIS) which is the main payload of STSAT-3. Each optical system consists of a Cassegrain telescope, a field lens and a 1:1 re-imaging lens system that is essential for providing a cold stop. The Cassegrain telescope is identical for both of two infrared cameras, but the field correction lens and re-imaging lens system are different from each other because of different bands of wavelength. The effective aperture size is 100mm in diameter and the focal ratio is f/5. The total length of the optical system is 300mm and the position of the cold stop is 25mm from the detector focal plane. The RMS spot size is smaller than $40{\mu}m$ over the whole detector plane.

• Korean Journal of Optics and Photonics
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• v.7 no.3
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• pp.191-195
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• 1996

A optical system of a movile LIDAR is designed for air pollution research. After the inverse Cassegrain type collimator, the laser beam falls on the mirror which serve for coinciding optical axis of laser beam and the receiving telescope. Then, it is directed into the atmosphere and back scattered radiation back to the receiving telescope by the scanning mirror. The unit of scanning mirror allows to rotate the mirror along the altitude 0$^{\circ}$~60$^{\circ}$, and the azimuth 0$^{\circ}$~360$^{\circ}$. The scanning mirror is not connected with the receiving telescope but placed on the roof of the mobile. The received beam is spatial filtered by a spatial filter and collimated by a fabric lens. Thereafter, the beam is devided into 2 channel for registration by a beam splitter. Each laser beam is transformed into an electrical signal by means of the photomultifier and then processed to be analyzed.