• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.453-454
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.463-464
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.293-294
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.51-52
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• 2008

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.4
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• pp.373-380
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• 2012

Purpose: The present study was performed to investigate a relationship between the stable centrations of spherical RGP lens and aspherical RGP lens on cornea and corneal eccentricity. Methods: Two RGP lenses with different designs were fitted in alignment, steep or flat on total 84 eyes having corneal eccentricity of 0.28~0.78. The stable centration of lenses on cornea was analyzed by taking photographs with a high-speed digital camera. Results: The stable centrations of spherical and aspherical RGP lenses in horizontal direction were decentrated to temporal side. More centration to median side was shown when corneal eccentricity was larger. The difference between the stable centrations of spherical and aspheric RGP lenses according to corneal eccentricity was bigger when the fitting state was flatter. The difference in the stable centrations of aspherical RGP lens was smaller than that of spherical RGP lens regardless of fitting status. The stable centrations of spherical and aspherical RGP lenses in vertical direction were located below corneal apex regardless of fitting status however, there was no significant difference analyzed by the variation of corneal eccentricity. However, there were many cases that RGP lenses were in upper eyelid with increasing corneal eccentricity. Conclusions: The consideration of corneal eccentricity is required for RGP lens fitting and manufacturing aspherical RGP lens since the stable centration of spherical RGP lens as well as aspherical RPG lens' centration was changed depending on corneal eccentricity.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.100-103
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• 2005

In this study, tool path control algorithm for aspherical surface grinding was derived and discussed. The aspherical surface actually means contact points between lens and tool. Tool positions are generally defined at the center of a tool, so there is difference between tool path and lens surface. The path was obtained from contact angle and relative position from the contact point. The angle could be calculated after differentiating an aspheric equation and complex algebraic operations. The assumption of the control algorithm was that x moves by constant velocity while z velocity varies. X was normal to the radial direction of lens, but z was tangential. The z velocities and accelerations were determined from current error and next position in each step. In the experiment, accuracy of the control algorithm was checked on a micro-precision machine. The result showed that the control error tended to be diminished when the tool diameter increased, and the error was under sub-micro level.

• 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.

• Journal of IKEEE
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• v.23 no.4
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• pp.1387-1392
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• 2019

Aspherical mirrors have lighter weight and better performance than spherical mirrors, but it is difficult to process their shape and measure the processing precision. Especially, large aperture aspherical mirrors mounted on satellites need high processing precision and long processing time. The computerized numerically controlled machine of gantry type has been used in polishing process, but it has difficulties in processing the complex shapes due to the lack of degrees of freedom. In order to overcome this problem we developed a polishing system using an articulated industrial robot. The system consists of tool path generating program, real-time robot monitoring, and control program. We show the performance of the developed system through the computer simulation and actual robot operation.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.10
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• pp.195-201
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• 2002

This paper deals with the precision grinding for aspherical surface of optical parts. A parallel grinding method using the spherical wheel was suggested as a new grinding method. In this method, the wheel axis is positioned at a $\pi$/4 from the Z-axis in the direction of the X-axis. An advantage of this grinding method is that the wheel used in grinding achieves its maximum area, reducing wheel wear and improving the accuracy of the ground mirror surface. In addition, a truing by the CG (curve generating) method was proposed. After truing, the shape of spherical wheel transcribed on the carbon is measured by the Form-Talysurf-120L. The error of the form in the spherical wheel which is the value ${\Delta}x$ and $R{^2}{_y}$ inferred from the measured profile data is compensated by the re-truing. Finally, in the aspherical grinding experiment, the WC of the molding die was examined by the parallel grinding method using the resin bonded diamond wheel with a grain size of ＃3000. A form accuracy of 0.16${\mu}m$ P-V and a surface roughness of 0.0067${\mu}m$ Ra have been resulted.