• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.137-143
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• 2008

The spherical glasses lenses are typically classified into two groups such as (+) diopter lens and (-) diopter lens by the refractive power index. The thermal deformation of a lens is occurred by external heat source and is changed respected to the diopter of a lens. In this paper, the thermal deformation of spherical glasses lenses were quantitatively measured by using ESPI (electronic speckle pattern interferometry) which has an advantage that the non-contact, non-destructive and precise deformation measurement is available due to the coherency characteristic. The temperature changes were measured by IR camera. It makes experiments over 14 types of the plastic glasses lenses. From the results, it was confirmed that the larger diopter lens showed the less thermal deformation in case of the (+) diopter lens. On the other hand, the thermal deformation of the (-) diopter lens was measured with uniform pattern when the same temperature changes were applied. Also, it was found that the thermnal deformation of the (+) diopter lens is less than that of the (-) diopter lens. Therefore, it is expected that when the thermal deformation is occurred to the various types of the lens, the variation of the focal length caused by the thermal distortion of a lens would be measured quantitatively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.289-292
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• 2007

To prevent the damage of glass lens molds and deterioration of glass lenses using in progressive GMP process, a thermal stress and a deformation of the glass lens molds at forming temperature should be considered in the design step. In this study, as a fundamental study to develop a multi cavity mold used in an aspheric glass lens molding, a heat transfer and a thermal stress analysis were carried out for the case of one cavity glass lens mold used in progressive GMP process. Finally, using analysis results, we estimated the thermal stress in a glass lens mold and predicted a modified height of guide ring that determines the forming height of a glass lens.

• Design & Manufacturing
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• v.2 no.6
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• pp.38-42
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• 2008

Recently, the demands of digital camera and miniature camera module for mobile-phone is increased significantly. Lenses which is the core component of optical products are made by the injection molding(plastic lens) or GMP(glass lens). Plastic lens is not enough to improve the resolution and performance of optic parts. Therefore, the requirement of glass lens is increased because it is possible to ensure the high performance and resolution. In this paper, the thermal stress analysis of 3 cavity GMP mold for molding glass lens was performed for estimating the thermal stress and amount of deformation. Finally, the modification plan based on the analysis results was deducted.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.12
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• pp.125-131
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• 2008

In the past, precision optical glass lenses were produced through multiple processes such as grinding and polishing, but mass production of aspheric lenses requiring high accuracy and having complex profile was rather difficult. In such a background, the high-precision optical GMP processes were developed with an eye to mass production of precision optical glass parts by molding press. Generally because the forming stage in a GMP process is operated at high temperature above $570^{\circ}C$, thermal stresses and deformations are generated in the aspheric glass lens mold that is used in GMP process. Thermal stresses and deformations have negative influences on the quality of a glass lens and mold, especially the height of the deformed glass lens will be different from the height of designed glass lens. To prevent the problems of a glass lens mold and the glass lens, it is very important that the thermal stresses and deformations of a glass lens mold at high forming temperature are considered at the glass molds design step. In this study as a fundamental study to develop the molds used in an aspheric glass lens fabrication, a heat transfer and a thermal stress analysis were carried out for the case of one cavity glass lens mold used in progressive GMP process. Finally using analysis results, it was predicted the height of thermally deformed guide ring and calculated the height of the guide ring to be modified, $64.5{\mu}m$. This result was referred to design the glass lens molds for GMP process in production field.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.2
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• pp.91-96
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• 2014

Aspheric lenses used in the thermal imaging are typically fabricated using expensive single-crystal materials (Ge and ZnS, etc.) by the costly single point diamond turning (SPDT) process. As a potential solution to reduce cost, compression molding method using chalcogenide glass has been attracted to fabricate IR optic. Thermal deformation of a molded lens should be compensated to fabricate chalcogenide aspheric lens with form accuracy of the submicron-order. The thermal deformation phenomenon of molded lens was analyzed ant then compensation using mold iteration process is followed to fabricate the high accuracy optic. Consequently, it is obvious that compensation of thermal deformation is critical and useful enough to be adopted to fabricate the lens by molding method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.354-354
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• 2008

Recently, due to the tremendous growth of media technology, demands of the aspheric glass lens which is a high-performance and miniaturized is gradually increasing. Generally, the aspheric glass lens is manufactured by GMP(Grass Molding Press) method using WC(tungsten carbide) mold core. In this study, the thermal deformation which occurs in the cooling step of GMP was considered, and it was compensated the form of mold core. The lens which was molded by compensated mold core was satisfied that can be applied to the actual specifications.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.1
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• pp.35-43
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• 2008

Aviation obstacle lights including controller for the safe night aviation service have applied to high voltage transmission line of which height is from $60{\sim}180 m$, Fresnel lens made by Augustine Fresnel have been applied to light houses, These Fresnel lens were applied to aviation obstacle lights and have been universally used, It was reported that Fresnel lens for aviation obstacle light was used in the first place in Korea in 1987, LEDs have recently been applied to aviation obstacle lights, So, the optimum physical design is essential to the design of aviation obstacle light. In this study, optical and three dimensional modeling of LED module and globe lens were performed, And thermal analysis due to LED thermal source and service thermal condition in high voltage transmission line was performed and was analyzed comparing with experiments, The optimum design process of medium intensity LED aviation obstacle lights was constructed with three dimensional modeling, thermal analysis, and thermal experimental technique.

• Journal of Power System Engineering
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• v.18 no.3
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• pp.87-92
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• 2014

This study is aimed at investigating the thermal behavior of immersion-cooled high power LED lighting engines. 3D CFD models have been generated for the numerical analysis. Five cases in terms of the configuration of LED chips have been explored for various passive cooling conditions of the lighting engine, i.e., the natural air convection with a lens, the natural air convection without a lens, the deionized water-immersion cooling condition with a lens. The numerical study reveals that the deionized water-immersion cooled lighting engine has nearly twice better thermal performance than the natural air convection cooled lighting engine containing a lens. The investigation has also demonstrated that the four chips configuration has the better thermal performance than the single chip configuration.

• Bulletin of the Korean Chemical Society
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• v.17 no.8
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• pp.682-685
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• 1996

Photothermal properties depend on the characteristics of energy transfer processes in solution. In this study, a time-resolved single beam thermal lens experiment in various solvents is employed to investigate the energy coupling effects which govern the energy transfer processes. Interestingly, it is observed that the behaviour of the photothermal propagation in solution depends on the property of solution and the concentration of solute in a single beam thermal lens configuration. These characteristics lead us to consider the solute-solvent coupling effects as well as the solvent-solvent interactions.

• Journal of the Optical Society of Korea
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• v.19 no.2
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• pp.182-187
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• 2015

This paper presents a new graphical method for selecting a pair of optical glasses to simultaneously achromatize and athermalize an imaging lens made of materials in contact. An athermal glass map that plots thermal glass constant versus inverse Abbe number is derived through analysis of optical glasses and plastic materials in visible light. By introducing the equivalent Abbe number and equivalent thermal glass constant, although it is a multi-lens system, we have a simple way to visually identify possible optical materials. Applying this method to design a phone camera lens equipped with quarter inch image sensor having 8-mega pixels, the thermal defocuses over $-20^{\circ}C$ to $+60^{\circ}C$ are reduced to be much less than the depth of focus of the system.