• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.1091-1096
• /
• 2007

This paper describes the development of a small lens molding system for manufacturing the small lens like lens of a cellular phone, a small digital camera and so on. In order to manufacture a small lens, firstly, the raw material for lens with spherical shape should be manufactured by processing a glass, secondly, the mold inserted the raw material for lens should be heated till its molding temperature in the electric furnace, finally, the small lens is manufactured by applying the force using pressuring control system. In this paper, the small lens molding system with the function of force control and velocity control was developed. It is composed of a electric furnace and its temperature control system, a pressuring control system, a body, and so on. The temperature characteristic test of the electric furnace, and the force and velocity characteristic test of the pressuring control system were carried out. It was confirmed that the developed system had good functions for manufacturing a small lens.

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.2
• /
• pp.57-64
• /
• 2008

This paper describes the development of a small lens molding system for manufacturing the small lens like lens of a cellular phone, a small digital camera and so on. In order to manufacture a small lens, firstly, the raw material for lens with spherical shape should be manufactured by processing a glass material, secondly, the mold inserted the raw material for lens should be heated till its molding temperature in the electric furnace, finally, the small lens is manufactured by applying the force using pressuring control system. In this paper, the small lens molding system with the function of force control and velocity control was developed. It is composed of an electric furnace and its temperature control system, a pressuring control system, a body, and so on. The temperature characteristic test of the electric furnace, the force and velocity characteristic test of the pressuring control system were carried out. It was confirmed that the developed system had good functions for manufacturing a small lens.

• Journal of the Korean Society for Precision Engineering
• /
• v.28 no.2
• /
• pp.202-210
• /
• 2011

The fabrication method of aspheric lens is changed from machining to press molding so as to improve the productivity. In the case of the press molding method, the temperature control of the molding die is most important, because the temperature of each molding die determines the quality of lens. But any practical method for direct measuring of the lens temperature and the die internal temperature is yet unknown. Besides, in the case of the press molding system in which the heating and pressing and cooing of a die is done at separate work stations, the lens productivity of the system for small lens is yet too low. The paper shows an improved structure of convective sequential system, the lens productivity of which is three times as many as the conventional convective system. To know the die internal temperature, numerical results are given using ANSYS. A new convective sequential system is developed and tested. Finally, the Taguchi method is applied in order to optimize the setting conditions of individual work station of the system.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.10a
• /
• pp.115-118
• /
• 2002

The purpose of this paper is to design a pick-up for the small form factor optical disk drive and to fabricate a micro-compensatory lens for the pick-up using the micro-compression molding process. At design stage, the optical elements including the objective lens and the compensatory lens are miniaturized. The height of pick-up and free working distance are designed as 2mm and 0.2% respectively. To analyze the fabricated micro-compensatory lens, the system was analyzed using the surface profile of the fabricated micro-compensatory lens and CODE V which is commercial software. The RMS wave front aberration of the system using fabricated micro-compensatory lens is 0.01677λ which is lower than Marechal's criterion, 0.07λ.

• Journal of the Korean Society for Precision Engineering
• /
• v.27 no.12
• /
• pp.67-74
• /
• 2010

The fabrication method of aspheric lens is changed from machining to press molding so as to improve the productivity. In the case of the press molding method, the temperature control of the molding die is most impotent, because the temperature of each molding die determines the quality of lens. But any practical method for direct measuring of the lens temperature and the die internal temperature is yet unknown. Besides, in the case of the press molding system in which the heating and pressing and cooing of a die is done at one work station, the cycle time for the system is yet too long. The paper shows an improved structure of radiant sequential system in which the heating and pressing and cooing of dies is done at individual work station so as to cut down the cycle time. To know the die internal temperature, numerical results are given using ANSYS. An experimental radiant sequential system is developed and tested. Finally, the Taguchi method is applied in order to optimize the setting conditions of individual work station.

• Journal of the Korean Society for Precision Engineering
• /
• v.31 no.7
• /
• pp.561-567
• /
• 2014

Precision injection mold is an essential element in order to manufacture small and precision plastic lenses used for phone camera. There are many critical factors to meet the requested specifications of high quality plastic lenses. One of the main issues to realize high quality is minimizing decenter value, which becomes more critical as pixel numbers increases. This study suggests the method to minimize decenter value by modifying ejecting structure of the mold. Decenter value of injection-molded lens decreased to 1 ${\mu}m$ level from 5 ${\mu}m$ by applying suggested ejecting method. Also, we also developed BIS (Built-in Sensor) based smart mold system, which has pressure and temperature sensors inside of the mold. Pressure and temperature profiles from cavities are obtained and can be used for deduction of optimal injection molding condition, filling imbalance evaluation, status monitoring of injection molding and prediction of lens quality.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2005.09a
• /
• pp.35-40
• /
• 2005

The demand for small and high-capacity optical data storage devices has rapidly increased. The areal density of optical disk is increased using higher numerical aperture objective lens and shorter wavelength source. A wafer-scale stacked micro objective lens with a numerical aperture of 0.85 and a focal length of 0.467mm for the 405nm blue- violet laser was designed and fabricated. A diffractive optical element (DOE) was used to compensate the spherical aberration of the objective lens. Among the various fabrication methods for micro DOE, the UV-replication process is more suitable for mass-production. In this study, an 8-stepped DOE pattern as a master was fabricated by photolithography and reactive ion etching process. A flexible mold was fabricated for improving the releasing properties and shape accuracy in UV-molding process. In the replication process, the effects of exposing time and applied pressure on the replication quality were analyzed. Finally, the shapes of master, mold and molded pattern were measured by optical scanning profiler. The deviation between the master and the molded DOE was less than 0.1um. The efficiency of the molded DOE was measured by DOE efficiency measurement system which consists of laser source, sample holder, aperture and optical power meter, and the measured value was $84.5\%$.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.10a
• /
• pp.266-270
• /
• 2007

Small injection molded articles such as lens and mobile product's parts are usually molded in multi-cavity mold. The problems occurred in multi-cavity molding are flow imbalance among the cavities. The flow imbalance affects on the dimensions and physical properties of molded articles. First of all, the origin of flow imbalance is geometrical imbalance of delivery system. However, even the geometry of delivery system is balanced well the cavity imbalance is being developed. This comes from the unsuitable operational conditions of injection molding. Among the operational conditions, injection speed is the most significant process variable affecting the filling imbalances in multi-cavity injection molding. In this study, experimental study of flow imbalance has been conducted for various injection speeds and materials. Also, the filling Imbalances were compared with CAE results. The dimensions and physical state of multi-cavity molded parts were examined. The results showed that the filling imbalances vary according to the injection speed and flow property of resins. Subsequently, the imbalanced filling and pressure distribution in the multi-cavity affect on the dimensions and physical states of molded parts.

• Korean Journal of Optics and Photonics
• /
• v.23 no.4
• /
• pp.154-158
• /
• 2012

In this paper, for low cost infrared optical equipment, we design and fabricate an infrared optical system for an uncooled detector using PGM(Precision Glass Molding) lenses. The designed infrared optical system has a good athermalization, and the material of all of its lenses is a chalcogenide glass suitable for the PGM method. In addition, we also fabricate the same infrared optical system using SPDT(Single Point Diamond Turning) lenses in order to measure the optical performance of PGM lenses. We measure the MTF(Modulation Transfer Function) of the two infrared optical systems which use the PGM lenses and the SPDT lenses. And then we compare and analyze the images of them both. As a result, we find that they have only a very small difference in optical performance. If the use of PGM lenses increases, we expect to reduce the cost of infrared optical equipment.

• Polymer(Korea)
• /
• v.32 no.6
• /
• pp.501-508
• /
• 2008

Small injection molded articles such as lens and mobile product parts are usually molded in multi-cavity mold. The problem occurring in multi-cavity molding is flow unbalance among the cavities. The flow unbalance affects the dimensions and physical properties of molded articles. First of all, the origin of flow unbalance is geometrical unbalance of the delivery system. However, even the geometry of the delivery system is well balanced, cavity unbalance occurs. This comes from the temperature distributions in the cross-section of runner. Temperature distribution depends upon injection speed because heat generation near runner wall is high at high injection speed. Among the operational conditions, injection speed is the most significant process variable affecting the filling unbalances in multi-cavity injection molding. In this study, experimental study of flow unbalance has been conducted for various injection speeds and materials. Also, the filling unbalances were compared with CAE results. The dimensions and weights of multi-cavity molded parts were examined. The results showed that the filling unbalances vary according to the injection speeds and resins. Subsequently, the unbalanced filling and pressure distribution in the multi-cavity affect the dimensions and physical states of molded parts.