• The Journal of the Acoustical Society of Korea
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• v.27 no.3
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• pp.140-148
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• 2008

In this study, a numerical method for a time-domain acoustic wave backscattering analysis is established based on a physical optics and a Fourier transform. The frequency responses of underwater targets are calculated based on physical optics derived from the Kirchhoff-Helmholtz integral equation by applying Kirchhoff approximation and the time-domain signals are simulated taking inverse fast Fourier transform to the obtained frequency responses. Particularly, the adaptive triangular beam method is introduced to calculate the areas impinged directly by acoustic incident wave and the virtual surface concept is adopted to consider the multiple reflection effect. The numerical analysis result for an acoustic plane wave field incident normally upon a square flat plate is coincident with the result by the analytic time-domain physical optics derived theoretically from a conventional physical optics. The numerical simulation result for a hemi-spherical end-capped cylinder model is compared with the measurement result, so that it is recognized that the presented method is valid when the specular reflection effect is predominant, but, for small targets, gives errors due to higher order scattering components. The numerical analysis of an idealized submarine shows that the established method is effectively applicable to large and complex-shaped underwater targets.

• Korean Journal of Optics and Photonics
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• v.15 no.4
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• pp.391-396
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• 2004

Spaceborne earth observation or astronomical payloads often use Cassegrain-type telescopes due to the limits in mass and volume. Precision optical alignment of such a telescope is vital to the success of the mission. This paper describes the simulated optical alignment methods using interferograms, wavefront error, and reverse-optimization method for different levels of alignment accuracy. It concludes with the alignment experiment results of a Cassegrain type spaceborne camera with 300mm entrance pupil diameter.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.10
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• pp.93-97
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• 2005

We have developed the FDSS (Fine Digital Sun Sensor) for the space technology of the STSAT-2 (Seience & Technology Satellite 2). The FDSS is firstly developed by using CMOS image sensor(CIS) in South Korea. The FDSS consists of the optics part, FPGA(Field Programable Gate Array) part, and MCU(Micro controller unit)part. This paper will focus on the optical characteristics of the optics part and describe the configuration of FDSS with the design of aperture. We also analyze the characteristic of optics about the pixel of the CMOS image sensor.

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.2
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• pp.99-103
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• 2003

This paper presents lens optimization of the resolution and the distortion for a four-element lens design. In order to have compact optical system, we used the tele-photo type lens composed of a positive and a negative power elements instead of retro-focus lens. The specifications of optical lens design are the focal length of 7.2 mm, the F/number of 2.8 and the field angle of $54.7^{\circ}C$. The MTF values are higher than 0.5 in the spatial frequency range up to 110 lp/mm for all of the designed object heights. Also, it is expected to fulfill all the requirements of a digital still camera lens and especially suited for building low-cost, compact digital cameras because of the low-profile property of the lens design.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.1
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• pp.31-35
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• 2008

Purpose: This study is to design a triplet optical system for CCTV camera lens. Methods: It was a telescopic lens with $5^{\circ}$ field angle, 56 mm focal length, 20 mm diameter, and 2/3 inches sized CCD array detector. Results: The performance of the subject optical system was evaluated by applying ray fan, spot diagram, and diffraction optical MTF. The wavelength was achromatized at Fraunhofer C, d and F-line, and both MTF and tangential & sagittal MTF shows more than 70% at spatial frequency of 50 linepairs/mm. Conclusions: The marketable triplet optical system for CCTV camera was designed and its utility was considered.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.5 no.2
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• pp.20-28
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• 1994

Theoretical radiation patterns for the corrugated horn antenna are analyzed by vector integral method and quasi-optics. The formular of the radiated fields for the corrugated horn antenna can be obtained by the potentials derived the equivalent current sources from hybrid fields at horn aperture and also calculated by the expanded mode set of Gaussian - Laguerre based on the quasi - optics. From comparison of the radiation patterns between two methods for a corrugated horn antenna designed on 85-115 GHz frequency range, the results are coincided well at center frequency but have some errors at each side frequencies 85 and 115 GHz.

• Korean Journal of Optics and Photonics
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• v.26 no.4
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• pp.187-194
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• 2015

A system of infrared camera optics with wide field of view and anamorphic lenses is proposed, and its validity verified through manufacture. The infrared camera produced provides a wide field of view of over 100 degrees in the horizontal direction, and an even greater magnification in the vertical direction. As a result, the system can have a wider surveillance range and improved detection ability at the same time. In addition, a new optomechanical automatic athermalization mechanism is proposed and applied to the infrared camera. Its performance and utility is proved through testing.

• Korean Journal of Optics and Photonics
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• v.29 no.3
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• pp.104-109
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• 2018

We explain the basic principle of transformation optics, and introduce several design techniques for transformation cavities that can maintain the characteristics of whispering gallery modes (WGMs) even if the cavity is strongly deformed from a circular shape. As a method of obtaining various transformation cavities under a specific conformal mapping, we suggest a method of parallel movement of the initial cavity domain, and a method of rotating the ellipse as a cavity domain. The internal wave pattern and the far-field output characteristics of several designed resonant modes are numerically calculated. From these results, it is confirmed that a variety of GRIN resonators are possible for a given conformal coordinate transformation.

• Korean Journal of Optics and Photonics
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• v.32 no.6
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• pp.296-305
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• 2021

This paper reports a study on the long axis performance of the line beam optics used in laser lift-off equipment for the OLED manufacturing process. The centration errors of the cylindrical lens are classified and defined in seven categories, and the measurement methods are presented. The cylindrical fly-eye lens is analyzed theoretically and experimentally to find the influence of the surface shape error and decentering error on the long axis performance of the line beam optics system. A future research direction is also presented to improve the long axis performance.

• Korean Journal of Optics and Photonics
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• v.25 no.5
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• pp.239-244
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• 2014

Retro-reflectors have been used for a wide range of applications such as traffic safety, special blinds, optical devices, etc. We analyzed the characteristics of the reflected light of a strap retro-reflector as a function of incidence angle. It is expected that various solar control structures may be designed more quantitatively using the characteristic chart we have prepared.