• Earthquakes and Structures
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• v.22 no.4
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• pp.401-419
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• 2022

A novel hybrid extreme machine learning-multiverse optimizer (ELM-MVO) framework is proposed to predict the liquefaction phenomenon in seismically excited tunnel lining inside the sand lens. The MVO is applied to optimize the input weights and biases of the ELM algorithm to improve its efficiency. The tunnel located inside the liquefied sand lens is also evaluated under various near- and far-field earthquakes. The results demonstrate the superiority of the proposed method to predict the liquefaction event against the conventional extreme machine learning (ELM) and artificial neural network (ANN) algorithms. The outcomes also indicate that the possibility of liquefaction in sand lenses under far-field seismic excitations is much less than the near-field excitations, even with a small magnitude. Hence, tunnels designed in geographical areas where seismic excitations are more likely to be generated in the near area should be specially prepared. The sand lens around the tunnel also has larger settlements due to liquefaction.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.3
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• pp.465-470
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• 2006

Coating are needed on ophthalmic lenses to enhance both the mechanical durability of the relatively soft plastic surface and the optical performance of lenses. Organic-inorganic hybrid materials as molar ratio of 3-glycidoxypropyltrimethoxysilane(GPTS), methyltrimethoxysilane(MTMS) and tetraethyl orthosilicate(TEOS) were used to improve the surface characteristics and the optical properties on allyl diglycol carbonate lenses. Coating for these plastics were at $140^{\circ}C$ for 4hrs, applied using the sol-grl process flow-coating technique. The coated lens properties of transmittance, adhesion, pencil hardness, abrasion resistance, hot water resistance and chemical resistance were investigated. The optimum properties was obtained when the ratio of GPTS : MTMS : TEOS was 1:1:2, respectively.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.258-265
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• 2002

In this paper, we design single and symmetrical double lenses with DOE. The specifications are the following : Image area is 4.8 mm $\times$ 3.6 mm, F/# is 2.8 and the overall length (from first lens surface to image plane) is 6.8mm. After comparing the optical performance and characteristic values, we determine that symmetrical double lenses are superior to single lenses. Symmetrical double lenses have the merits of fewer zones, weaker flare, and smaller distortion than single lenses.

• Korean Journal of Optics and Photonics
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• v.28 no.5
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• pp.241-249
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• 2017

This paper presents the design and evaluation of the optical system for an uncooled thermal-imaging camera. The operating wavelength range of this system is from $7.7{\mu}m$ to $12.8{\mu}m$. Through optimization, we have obtained a LWIR (Long Wave Infrared) optical system with a focal length of 5.44 mm, which consists of four aspheric surfaces and two diffractive surfaces. The f-number of the optical system is F/1.2, and its field of view is $90^{\circ}{\times}67.5^{\circ}$. The hybrid lens was used to balance the higher-order aberrations, and its diffraction properties were evaluated by scalar diffraction theory. We calculated the polychromatic integrated diffraction efficiency, and the MTF drop generated by background noise. We have evaluated the thermal compensation of a LWIR fixed optical system, which is optically passively athermalized to maintain MTF performance in the focal depth. In conclusion, these design results are useful for an uncooled thermal-imaging camera.

• Korean Journal of Optics and Photonics
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• v.12 no.3
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• pp.240-249
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• 2001

A high speed ultra-compact lens with a diffractive optical element (DOE) is designed, which can be applied to mobile communication devices such as IMT2000, PDA, notebook computer, etc. The designed hybrid lens has sufficiently high performance of less than f/2.2, compact size of 3.3 mm (1st surf. to image), and wide field angle of more than 30 deg. compared with the specifications of a single lens. By proper choice of the aspheric and DOE surface which has very large negative dispersion, we can correct chromatic and high order aberrations through the optimization technique. From Seidel third order aberration theory and Sweatt modeling, the initial data and surface configurations, that is, the combination condition of the DOE and the aspherical surface are obtained. However, due to the consideration of diffraction efficiency of a DOE, we can choose only four cases as the optimization input, and present the best solution after evaluating and comparing those four cases. On the other hand, we also report dramatic improvement in optical performance by inserting another refractive lens (so-called, field flattener), that keeps the refractive power of an original DOE lens and makes the petzval sum zero in the original DOE lens system. ystem.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.53-56
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• 2009

반사와 굴절이 합쳐진 새로운 형태의 하이브리드 태양광 집광 장치로 기존 집광 장치에 비해 초점 거리가 짧게 설계되었다. 프레넬 렌즈 형태의 굴절부와 프레넬형의 다수의 포물선 반사경이 공통으로 후면 초점(rear focus)을 가지도록 배치하여 기존 프레넬 렌즈만으로 구성된 것보다 선형 집광의 경우는 3배, 점 집광의 경우는 10배 이상 집광비를 높일 수 있다.아울려 이를 이용한 선형 집광형 발전 시스템과 점형 집광 장치는 나름대로 장점을 가진다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.782-787
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• 2002

In optical disk drives (ODD), the demands of high data density and high speed have been increasing rapidly to achieve high data capacity and data transfer rate. The short wavelength laser, High NA objective lens, and high track following performance are needed to raise data density and data rate. For high-performance actuator, the improvement of linearity and acceleration become more important. Also, 3-axis actuator for active tilt compensation is introduced to overcome the decrease in disk tilt tolerance which is induced by short wavelength laser. In this paper, a hybrid type 3-axis actuator is presented and a new yoke structure, which can reduce the interaction between yoke and moving magnet, is designed to keep the efficiency of magnetic circuit. Experimental results show the validity of the yoke in the hybrid type actuator.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.163-164
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• 2000

We discuss the design and fabrication of CCD or C-MOS imaging lenses with hybrid diffractive / refractive optics. The hybrid lenses are made of optical grade plastic materials. We have been able to significantly reduce the number of elements while maintaining very high optical quality. This paper describes the conception, design, fabrication and evaluation of hybrid lenses in comparison with conventional refractive lenses. The new lens has excellent optical quality, very light weight, compact size and low manufacturing cost.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.6
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• pp.636-641
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• 2014

This paper discusses the fabrication process for a Nipkow disk using micro-lens and pinhole disks. The confocal measuring system that uses the Nipkow disk has the advantage in measuring speed, because the Nipkow disk can simultaneously provide confocal images of all pixels in a CCD camera without requiring a lateral scanning unit. A micro-lens configuration, which focuses illumination on a pinhole, overcomes the low optical efficiency of the Nipkow disk system and allows its use in practical applications. This paper describes how to design the Nipkow disk in terms of numerical aperture, particularly for measuring the height of solder bumps in packaging application and for hybrid processes combining mechanical and semiconductor processes.

• Proceedings of the Optical Society of Korea Conference
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• 2007.02a
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• pp.135-136
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• 2007