• Journal of Korean Ophthalmic Optics Society
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• v.12 no.4
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• pp.87-90
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• 2007

To manufacture the lens mold used in producing polycarbonate (PC) lenses, the core manufacturing is needed and this core manufacturing is generally performed by diamond turning machine (DTM) or computer numerical control (CNC) lathe. The numerical data about the lens core feature is necessarily needed for operating of these devices. Therefore, we developed the program which calculate the numerical data about the lens core feature. The program was composed to be able to input aspherical coefficients of lens feature, display the graph of lens feature, and save the numerical data file.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.1
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• pp.92-99
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• 2014

An aspherical lens, which resolves several problems with a spherical lens,typically serves asa key part of an optical system. Generally, an aspherical lens is fabricated using a diamond turning machine or by mean of injection molding. However, residual stress and/or tool marks can arise when using a commercial fabricating method such as DTM or injection molding. A polishing process, thus, is commonly used to obtain a high-precision aspherical lens. In this study, a polishing method using MR fluid was applied to minimize several problems, in this case residual stress and the creation of tool marks, during the cutting process. The MR polishing system was developed to polish aspherical lenses. A series of experiments were performed to obtain a very fine surface roughness. PMMA (the lens material for molding) was used as a workpiece, and the gap size, magnetic field intensity, wheel speed and feed rate were selected as the parameters in this study. Finally, a very fine surface roughness of Ra=2.12nm was obtained after MR polishing.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.851-856
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• 2005

The precision fabrication of aspherical lenses is increasingly required for the latest applications of compact and high resolution video-recording or camera systems. Micro-optical components, including micro-spherical or aspherical lenses and reflecting mirrors, are generally required to be manufactured with high shape accuracy, extremely low surface roughness and no surface damage. To meet the needs of the precision fabrication system, a bed which supports the micro aspherical lens fabrication machines stably and safely is required. In this study, the thickness of the ribs of the bed is optimized using the CAD integrated optimal design system, a virtual DS program.

• Korean Journal of Optics and Photonics
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• v.26 no.6
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• pp.299-305
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• 2015

Using Snell's Law without approximation, we analyzed focal points for parallel rays incident upon the cornea of a human eye. To calculate a ray's incident angle versus incident height for focusing on the same point, we used the ray reverse tracing method. We derived the theoretical conditions for an aspherical lens to remove the spherical aberration caused by a human eye. In this research, we held the rear surface of the lens to be spherical, for simple calculation, and calculated the lens curvature of the front surface to design an aspherical surface.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.2
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• pp.14-20
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• 2005

This paper describes a dwell time calculation algorithm for polishing tool path generation in the small toot polishing process of the axis-symmetrical lens. Generally dwell time control in the polishing machines means that small polishing tool stays for a dwell time at the specific surface position to get the expected polishing depth. Polishing depth distribution on an aspherical lens surface consists of the superposition of the local polishing depth at the each dwell position. Therefore, tool path generation needs each dwell time together with tool positioning data during the polishing tool movements on the aspherical lens surface. The linear algebraic equation of removal depth removal matrix and dwell time is formulated. Parametric effects such as the dwell d interval are simulated to validate the dwell time calculation algorithm.

• Journal of the Optical Society of Korea
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• v.13 no.2
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• pp.213-217
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• 2009

The transcription characteristics of the mold surface in the molding of aspherical 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. For the form topography, the molded lens showed a transcription ratio of 93.4% against the mold, which is obtained by comparing the form error (PV) values of the mold and the molded lens. The transcription characteristics of the roughness topography were ascertained by bearing ratio analysis.

• Design & Manufacturing
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• v.2 no.1
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• pp.33-38
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• 2008

As consumer in optics, electronics, aerospace and electronics industry grow, the demand for ultra precision aspherical surface lens increases higher. Precision turning with single-diamond tools has a long history of development for fabrication of optical quality surfaces since the advent of aerostatic rotary spindles and precise linear motion guide ways. To enhance the precision and productivity of ultra precision aspherical surface micro lens, the following specification of ultra precision grinding system is required: the highest rotational speed of the grinder is 100,000rpm and its turning accuracy is $0.1{\mu}m$, positioning accuracy is $0.1{\mu}m$. The development process of the grinding system for the ultra precision aspherical surface micro lens for optoelectronics industry is introduced. In the work reported in this paper, an intelligent grinding system for ultra precision aspherical surface machining was designed by considering the factors affecting the surface roughness and profiles accuracy. An aerostatic form was adopted to build the spindle of the workpiece and the spindle of grinder and ultra precision LM guide way was adopted in this system. And this paper deals with mirror grinding of an aspheric surface micro lens by resin bonded diamond wheel and spherical lens of BK7. It results was that a form accuracy of $0.6{\mu}m$ P-V and a surface roughness of $0.006{\mu}m$ Rmax.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1737-1740
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• 2005

As the various manufacturing technology of optical glass is developed, the aspherical lenses are applied to many fields. However, It is still very difficult to manufacture glass lens because of the high cost and the short life of core. In recent years, the demands of the aspherical glass lenses increase since it is difficult to obtain the desirable performance in the plastic lens. In the glass mold lens, it has merits of high productivity and reproductivity since lens is manufactured by the only forming with high precision mold. The fabricating conditions for glass mold lens are glass surface that does not cause fusion, viscosity of 108-1013 poise for the $0.2{\mu}m$ accuracy, and viscoelasticity for the roughness less than 100 angstrom. In this thesis, ultra-precision grinding characteristics of tungsten carbide for forming the aspherical glass lens core were studied and the result of it is applied to manufacture the tungsten carbide-base core of the glass lens used to the laser scanning unit and the camera phone.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1910-1913
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• 2005

As the various manufacturing technology of optical glass is developed, the aspherical lenses are applied to many fields. However, It is still very difficult to manufacture glass lens because of the high cost and the short life of core. In recent years, the demands of the aspherical glass lenses increase since it is difficult to obtain the desirable performance in the plastic lens. In the glass mold lens, it has merits of high productivity and reproductivity since lens is manufactured by the only forming with high precision mold. The fabricating conditions for glass mold lens are glass surface that does not cause fusion, viscosity of 108-1013 poise for the $0.2{\mu}m$ accuracy, and viscoelasticity for the roughness less than 100 angstrom. In this paper, ultra-precision grinding characteristics of tungsten carbide for forming the aspherical glass lens core were studied and the result of it is applied to manufacture the tungsten carbide-base cores of the glass lens used to the laser scanning unit and the camera phone.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.307-312
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• 2005

As the various manufacturing technology of optical glass is developed, the aspherical lenses are applied to many fields. However, It is still very difficult to manufacture glass lens because of the high cost and the short life of core. In recent years, the demands of the aspherical glass lenses increase since it is difficult to obtain the desirable performance in the plastic lens. In the glass mold lens, it has merits of high productivity and reproductivity since lens is manufactured by the only forming with high precision mold. The fabricating conditions for glass mold lens are glass surface that does not cause fusion, viscosity of 108-1013 poise for the $0.2{\mu}m$ accuracy, and viscoelasticity for the roughness less than 100 angstrom. In this thesis, ultra-precision grinding characteristics of tungsten carbide for forming the aspherical glass lens core were studied and the result of it is applied to manufacture the tungsten carbide-base core of the glass lens used to the laser scanning unit and the camera phone.