• Korean Journal of Optics and Photonics
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• v.11 no.2
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• pp.73-79
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• 2000

We measure a beam diameter of scan and sub-scan direction of LSD (Laser Scanning Urnt) which uses $fheta$ lens produced by injecLion molding method as a scanning lens. While the measured beam diameter in scan direction, which is $62muextrm{m}$ to $68\mu\textrm{m}$, shows similar size comparing to the design beam diameter, the sub-scan beam diameter shows sIzable beam diameter deviation as much as 37 11m ranging from $78\mu\textrm{m}$ to $115\mu\textrm{m}$. Injection molding lens has the surface figure error due to the shrinkage III the cooling time and the internal distortion (birefringence) due to the uneven cooling conditIOn so that these bring about wavefront aberration (i.e., the enlargement of beam size), and are eventually expre~sed as the deterioration of the pdnting image. In this paper. we first measure and analyze beam diameter, birefringence (polanzation ratio), and asphedcal figure error of mIens in order to know the principle cause of the beam diameter deviation in sub-scan directIOn. And Lhen. through the analysis of a designed depth of focus and a calculated field curvature (imaging position of the optical axis directIon) using the above figure elTor data, we know Lhat the birefringence IS the main factor of sizable beam diameter deVIation in sub-scan direction. ction.

• 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.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.3
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• pp.117-124
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• 2007

In order to operate CD and DVD compatibly in a pickup system, the objective lens comprise diffractive optical element(DOE) zone and aspheric curvature on its lens surface. The DOE objective lens is effective to simplify this dual-purpose pickup system of the 655nm and 785nm wavelength by using only one lens, but requires more precision manufacturing process and system due to the complicated shape. This paper presents the overall manufacturing process of this objective lens and describes main parameters in each process, for the correction of the aspheric surface in its core, the shrinkage compensation after injection molding, and the uniformity compensation by adjusting molding conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.57-60
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• 2002

The high precision spindle is essential fer mass and low cost production of aspherical glass lens. Especially, in the grinding process of micro glass lens the performance of the spindle determine the machined surface quality. For the aspheric micro glass lens grinding, we design and make a high precision spindle. We use air bearings for high speed and low motion errors of the spindle. And the driving mechanism is an air turbine to remove heat generation. In this study, we make basic performance requirements of the spindle through benchmarking. And we confirm the requirements by basic machining test. We test air consumption, static stiffness, run-out and vibration of the spindle.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.21-28
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• 2007

Injection molding process factors such as molding temperature, injection pressure, flow rate and flow velocity, must be controlled properly in filling and packing phases in the injection molding process. In this study, effects of these factors on the injection molding were investigated through the flow analysis for birefringence and refractive index for pickup lens. This paper presents the birefringence and refractive index reduced with increasing the holding pressure and also the holding pressure time. And there are interaction with birefringence and fill time in the injection process. The optimal conditions through DOE are validated by using injection molding analysis.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.4
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• pp.112-118
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• 2008

In order to meet the optical performance in the process of the micro lens manufacturing with plastics, it is important to embody accuracy in shape and surface roughness to the intended design. Since it is difficult to machine exactly the mold core of lens fit to the designed shape, in this paper, a simple program using MATLAB is developed for shape correction of the mold core after first machining it. This program evaluates correction parameters(aspheric coefficients and curvature) and generates aspheric NC data for compensating the core surface in prior machining process. The program provides the way to manufacture plastic injection molding lens with aspheric shape of high precision, and is expected to be effective for correction and to shorten the processing time.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.427-427
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• 2007

The global applications of aspherics surfaces will expand rapidly on the electronics, optical components, communications, aerospace, defense, and medical optics devices etc. Especially, Asymmetric aspheric prism lens is one of the important parts in HMD(Head Mounted Display) because it affects dominantly on the optical performance of HMD. The mold core is the most important device to produce the plastic lenses by injection molding method. In this study, the mold cores for asymmetric aspheric prism lens were processed using fly-cutting method which is kind of the ultra precision processing and form accuracy and surface roughness of the cores were measured.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.1 s.178
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• pp.113-120
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• 2006

This paper proposed the control algorithm fur aspheric surface grinding and was verified by the experiment. The functions of the algorithm were simultaneous control of the position and interpolation of the aspheric curve. The non-linear formula of the tool position was derived from the aspheric equations and the shape of the tool. The function was partitioned by an certain interval and the control parameters were calculated at each control section. The movement in a session was interpolated with acceleration and velocity. The position error was feed-backed by rotary encorder. The concept of feedback algorithm was correcting position error by increasing or decreasing the speed. In the experiment, two-axis machine was controlled to track the aspheric surface by the proposed algorithm. The effect of the control and process parameters was monitored. The result showed that the maximum tracking error was under sub-micro level for the concave and convex surfaces.

• 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.

• Journal of the Korean Society for Precision Engineering
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• v.6 no.4
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• pp.11-20
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• 1989

마이크로 일렉트로닉스(Microelectronics)를 중심으로 하는 산업혁명이 진행되고 있는 시점에서 전자, 광학 또는 신소재 부품에 대한 형상과 치수 또는 표면거칠기에 대한 정확도와 정밀도가 엄격하게 요구되고 있다. 예를 들어 경취 재료인 반도체의 웨이화( w-afer), 수정진동자 자기헷트, 비구면렌즈 또는 연질 금속의 레이저빔(Laser Beam) 프린터 용 포리곤 밀러(Polygon Mirror), 자기디스크, 복사기용 드럼(drum), 레저기기용 반사밀러 등 가공정밀도를 향상시키기 위해서는 과거의 가공기술을 대치할 수 있는 새로운 초정밀가공 기술의 도입이 활발하게 진행되고 있다. 경취성 재료의 초정밀가공은 지금까지는 랩핑(lappi- ng), 폴리싱(polishing)의 가공기술이 주체였으나, 최근의 엄격한 부품정밀도에 대응하기 위하여 전가공을 초정밀 연삭가공으로 평면도,표면거칠기, 가공변질층을 향상시키고 다듬질 가공은 폴리싱으로 하여 표면거칠기를 향상시켜야 하는 가공기술이 보급되고 있다. 일반연질 금속의 다듬질가공은 유리지립을 이용하는 랩핑이나 폴리싱으로 다듬질 가공을 진행하고 있었 으나 형상정도와 표면정밀도를 동시에 얻는다는 것이 어렵고 또 가공시간이 너무 길어서 매우 고가인 것이 되고 말았다. 그러나 유리에서 연질금속으로 재료를 전환시키고 저가격화, 양산 화의 요구, 정밀도 향상과 부품의 안정화 등등 여러 이유로서 다아아몬드(Diamond) 공구로 mirror surface 를 만드는 초정밀 경면연삭 가공기술(precision turning with diamond)의 발달 로 이제는 완전히 새로운 가공기술로 대치되고 말았다. 다이아몬드에 의한 초정밀절삭은 공구 끝이 매우 예리하고 마모가 매우 적은 단결정 다이아몬드를 이용하고 절삭가공 기계는 운동정도 를 피가공물에 정확히 전사 시키는 방법이며 따라서 가공기계는 고도의 운동정밀도가 요구되며 그외에 강성, 진동, 열변이, 제어면에서 엄격한 검도가 있어야 한다.