• 한국재료학회지
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• 제32권12호
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• pp.515-521
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• 2022

Various types of optical materials and devices used in special environments must satisfy durability and optical properties. In order to improve the durability of zinc sulfide multispectral (MS ZnS) substrates with transmission wavelengths from visible to infrared, Ge-Sb-Se-based chalcogenide glass was used as a sealing material to bond the MS ZnS substrates. Wetting tests of the Ge-Sb-Se-based chalcogenide glass were conducted to analyze flowability as a function of temperature, by considering the glass transition temperature (T_g) and softening temperature (T_s). In the wetting test, the viscous flow of the chalcogenide glass sample was analyzed according to the temperature. After placing the chalcogenide glass disk between MS ZnS substrates (20 × 30 mm), the sealing test was performed at a temperature of 485 ℃ for 60 min. Notably, it was found that the Ge-Sb-Se-based chalcogenide glass sealed the MS ZnS substrates well. After the MS ZnS substrates were sealed with chalcogenide glass, they showed a transmission of 55 % over 3~12 ㎛. The tensile strength of the sealed MS ZnS substrates with Ge-Sb-Se-based chalcogenide glass was analyzed by applying a maximum load of about 240 N, confirming its suitability as a sealing material in the far infrared range.

• Journal of the Optical Society of Korea
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• 제19권5호
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• pp.531-536
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• 2015

This paper presents a new graphical method for selecting a pair of optical glass and housing materials to simultaneously achromatize and athermalize a multilens system composed of many elements. To take into account the lens spacing and housing, we quantify the lens power, chromatic power, and thermal power by weighting the ratio of the paraxial ray height at each lens to them. In addition, we introduce the equivalent single lens and the expanded athermal glass map including a housing material. Even though a lens system is composed of many elements, we can simply identify a pair of glass and housing materials that satisfies the athermal and achromatic conditions. Applying this method to design a black box camera lens equipped with a 1/4-inch image sensor having a pixel width of $2{\mu}m$, the chromatic and thermal defocusings are reduced to less than the depth of focus, over the specified ranges in temperature and frequency.

• 소성∙가공
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• 제12권4호
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• pp.296-301
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• 2003

Though a glass tens has outstanding optical performance, it has not been widely used because manufacturing process shows poor productivity and high cost. However, press-forming method of glass lens overcomes these disadvantages with mass production. When glass lens is produced by press-forming method using closed die, it is needed that the volume of glass lens preform is precisely measured in order to prevent incomplete products and to increase in life of die. The present. paper shows the shortcoming of forming process with closed die, and performs FEM simulation of forming process with open die in order to overcome this shortcoming. The design parameters of open die are selected on the basis of assembly with optical module and maintenance of optical performance. FEM simulation is carried out with selected parameter of open die and two basic preform. According to distribution of effective strain in glass lens, optical property of glass lens formed at each set of die and preform is compared.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.363-366
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• 2008

The transcription characteristics in the molding of aspheric glass lenses for camera phone modules have been investigated experimentally. The surface topographies of both the form and the roughness were compared between the mold and the molded lens. The molded lens showed a transcription ratio of 93.4%, which is obtained by comparing the form accuracy (PV) values of the mold and the molded lens. The transcription of the roughness topography was ascertained by bearing ratio analysis.

• Journal of the Optical Society of Korea
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• 제19권2호
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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.

• Current Optics and Photonics
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• 제7권3호
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• pp.273-282
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• 2023

This paper presents a new method for redistributing effectively the first orders of each lens element to achromatize and athermalize an optical system, by introducing a novel method for adjusting the slope of an achromatic and athermal line. This line is specified by connecting the housing, equivalent single lens, and aberration-corrected point on a glass map composed of available plastic and glass materials for molding. Thus, if a specific lens is replaced with the material characterized by the chromatic and thermal powers of an aberration-corrected point, we obtain an achromatic and athermal system. First, we identify two materials that yield the minimum and maximum slopes of the line from a housing coordinate, which specifies the slope range of the line spanning the available materials on a glass map. Next, redistributing the optical first orders (optical powers and paraxial ray heights) of lens elements by moving the achromatic and athermal line into the available slope range of materials yields a good achromatic and athermal design. Applying this concept to design a mobile-phone camera lens, we efficiently obtain an achromatic and athermal system with cost-effective material selection, over the specified temperature and waveband ranges.

• 한국안광학회지
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• 제6권1호
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• pp.145-148
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• 2001

안경렌즈 절삭용 재료의 파괴인성과 경도를 향상시키기 위하여 glass상을 함유한 탄화규소계 복합재료를 개발하여 그 기계적 물성과 특성을 연구하고자 하였다. glass상을 갖는 탄화규소를 $1810^{\circ}C$에서 2시간, 25 MPa의 조건에서 일축 가압소결 공정으로 안경렌즈 절삭용 시편을 제조하였다. 파괴인성과 경도를 측정하여 전에 실험한 결과의 기계적 특성과 비교하였다. 본 연구에서 연구된 안경렌즈 절삭용 시편의 대표적인 경도와 파괴인성은 각각 12 GPa과 $5.1MPa{\cdot}m^{1/2}$ 이었다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1491-1495
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• 2004

In this paper, resonant ultrasound spectroscopy(RUS) was used to determine the natural frequency of a spherical and a aspherical lens. The objective of the paper is to evaluate defect and shape error by using nondestructive evaluation method with Resonant Ultrasound Spectroscopy(RUS). The principle of RUS is that the mechanical resonant frequency of the materials depends on density, and the coefficient of elasticity. We evaluated existence of flaws through comparison with resonant frequency of a spherical and a aspherical lens. The spherical glass lenses were made of BK-7 glass, one's diameter in 2mm and 5mm. The polished spherical glass lenses had no deflection or a deflection below 2.0${\mu}{\textrm}{m}$. Also, The aspherical lens were made of same material and ones diameter in 7mm and thickness in 3.4mm. In the experiment, we were performed to investigate relationship between frequency measuring parameter($\beta$) and mass of each specimens. The difference between resonant frequency and mode of aspherical glass lens which has no defect was distinguished from aspherical glass lens which has some defects.

• 한국정밀공학회지
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• 제24권4호
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• pp.115-122
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• 2007

Recently, remarkable progress has been made in both technology and production of optical elements including aspheric lens. Especially, requirements for machining glass materials have been increasing in terms of limitation on using environment, flexibility of material selection and surface accuracy. 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 process was developed with an eye to mass production of precision optical glass parts by molding press. This GMP process can produce with precision and good repeatability special form lenses such as camera, video camera, aspheric lens for laser pickup, $f-\theta$ lens for laser printer and prism, and me glass parts including diffraction grating and V-grooved base. GMP process consist a succession of heating, forming, and cooling stage. In this study, as a fundamental study to develop molds for GMP used in fabrication of glass lens, we conducted a glass lens forming simulation. In prior to, to determine flow characteristics and coefficient of friction, a compression test and a compression farming simulation for PBK40, which is a material of glass lens, were conducted. Finally, using flow stress functions and coefficient of friction, a glass lens forming simulation was conducted.

• 한국안광학회지
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• 제17권2호
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• pp.119-126
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• 2012

목적: 안경 렌즈 코팅 막을 불화수소산을 이용하여 상온에서 단시간 화학적으로 식각한 뒤 코팅 막과 렌즈 원재료의 변화를 살펴보고자 하였다. 방법: GRAY 70%로 염색된 vinyl ester계 고분자(Lens A)와 thiourethane계 고분자렌즈(Lens B)를 불화수소산을 이용해 5분, 10분 또는 15분 동안 식각한 뒤 재료의 기계적 물성과 하드코팅과 반사방지코팅 등 코팅 막의 손상 정도, 그리고 굴절률 광투과율 등 렌즈의 특성 변화를 관찰하였다. 결과: 두 재료 모두 식각 전과 후의 굴절력에는 큰 변화가 없었지만 반사방지코팅과 하드코팅이 차례로 제거되었고 렌즈 표면에도 손상을 주어 UV 투과율이 증가되었으며 기계적 물성은 소하였다. 화학적 식각으로 인한 렌즈의 물성 변화는 thiourethane계 고분자 렌즈에서 더 크게 나타났다. 결론: 고분자 재료의 특성에 따라 불화수소산에 대한 반응성이 다르기 때문에 식각에 따른 렌즈 자체의 물성 변화가 다르게 나타남을 알 수 있었다.