• Title/Summary/Keyword: birefringence

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Numerical Simulation of Flow-Induced Birefringence in Injection Molded Disk

  • Lee H. S.;Shyu G. D.;Isayev A. I.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.41-47
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    • 2003
  • This study is an attempt to understand the birefringence and stress development in an injection molded disk. A computer code was developed to simulate all three stages of the injection molding process - filling, packing and cooling by finite element method. The constitutive equation used here was compressible Leonov model. The PVT relationship was assumed to follow the Tait equation. The flow-induced birefringence was related to the calculated flow stresses through the linear stress-optical law. The predicted birefringence was in good agreement with the experimental results.

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Numerical simulation of flow-induced birefringence in injection molded disk

  • Shyu, Goang-Ding;Avraam I. Isayev;Lee, Ho-Sang
    • Korea-Australia Rheology Journal
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    • v.15 no.4
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    • pp.159-166
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    • 2003
  • This study is an attempt to understand the birefringence and stress development in an injection molded disk. A computer code was developed to simulate all three stages of the injection molding process filling, packing and cooling by finite element method. The constitutive equation used here was compressible Leonov model. The PVT relationship was assumed to follow the Tait equation. The flow-induced birefringence was related to the calculated flow stresses through the linear stress-optical law. The predicted birefringence was in good agreement with the experimental results.

Effect of Insulation Layer on Birefringence and Land-groove Pattern in DVD-RAM Substrate (단열층이 DVD 기판의 복굴절 및 전사성에 미치는 영향)

  • Kim, Y.;Seong, K.;Kang, S.
    • Proceedings of the KSME Conference
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    • pp.432-437
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    • 2001
  • It is necessary to improve mechanical and optical porperties in the optical disk substrates as the information storage devices with high storage density using blue laser are being developed. Injection compression molding is regarded as the most suitable process to manufacture optical disk substrates for quality recording and read-out. In the present research, the effects of processing conditions and the insulation layer thickness on gapwise birefringence and the land-groove pattern were investigated. It was found that the values of the birefringence distribution were very sensitive to mold temperature history, and the level of birefringence reduced and, furthermore, the quality of replication was improved due to the insulation layer.

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A Study Birefringence of Injection Molding for Plastics Aspheric Lens (플라스틱 비구면 사출렌즈의 복굴절에 관한 연구)

  • Jun, Yoo-Tae;Hyun, Dong-Hoon
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.15 no.1
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    • pp.108-112
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    • 2006
  • A Study of birefringence in an aspheric lens of injection molding became more important to improve its optical properties. In the present study, the experimental study was carried out to investigate the relationship between birefringence and injection molded conditions. The processing factors are conditions include packing pressure, packing time, injection speed, melt temperature of optical resin and wall temperature. Birefringence was observed figures by using a polarizer in light. This experiments were carried out using the simulation software and injection molding machine.

A Study on The Birefringence Measurement in Precision Optical Product (정밀 광학 부품의 복굴절 측정 방법에 관한 연구)

  • Min, In Ki;Ko, Young Bae;Kwon, Chang Oh;Yoon, Kyung Hwan
    • Journal of the Korea Society of Die & Mold Engineering
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    • v.6 no.1
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    • pp.90-94
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    • 2012
  • Recently, injection molding process became more popular than ever to produce large quantities of high precision products. Extensive studies have been conducted for reducing the residual stresses and birefringence in injection-molded optical products. Flow-induced and thermally-induced stresses and birefringence have been found as two main sources during injection molding process. Generally, quantitative value of birefringence can be measured with polarizing microscope using the compensator. However, it is difficult to measure low order retardation with microscope, so developing a measurement system for low order optical path difference is in need. In the present paper, a system using Photo Elastic Modulator (PEM) is demonstrated to measure low phase retardation in injection-molded products.

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The Effect of Various Molding Methods for Precision Optical Products Using Birefringence Analysis (정밀 광학부품의 복굴절 분석을 통한 각종 성형법의 영향에 관한 연구)

  • Min, I.K.;Cho, S.W.;Yoon, K.H.
    • Transactions of Materials Processing
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    • v.22 no.1
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    • pp.48-53
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    • 2013
  • As the adoption of injection molding technology increases, injected-molded optical products require higher dimensional accuracy and optical stability than ever before. In the present study, four kinds of molding methods, i.e., conventional injection molding (CIM), injection/compression molding (ICM), rapid heat and cooling the mold(RHCM) and rapid injection/compression molding (RICM) were selected in order to investigate the optical anisotropy of a 7 inch Light Guide Plate(LGP) by examining the gap-wise distribution of birefringence and the extinction angle. The results indicate that the compression process can decrease flow-induced birefringence over the whole region and that rapid heating can decrease the birefringence level better than conventional molding. In addition, for the combination of compression and rapid heating a reversal flow was detected from the distribution of the extinction angle near the gate.

A High Birefringent Polymer Terahertz Waveguide: Suspended Elliptical Core Fiber

  • Wang, Jingli;Chen, Heming;Shi, Weihua
    • Journal of the Optical Society of Korea
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    • v.18 no.5
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    • pp.453-458
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    • 2014
  • A novel high birefringent polymer terahertz (THz) fiber with a suspended elliptical core is proposed in this paper. The introduction of an elliptical core can enhance asymmetry to realize high mode birefringence, and a large porous outer cladding effectively isolates the core-guided mode from interacting with the surrounding environment. A full-vector finite element method(FEM) is used to analyze the characteristics of the THz fiber. Simulation results show that the suspended elliptical fiber exhibits high mode birefringence on a level of $10^{-2}$ over a wide frequency range, and an extremely large mode birefringence(${\approx}0.06226$) is obtained when ellipticity is 0.2. Moreover, a suspended hollow elliptical core fiber is also discussed for the purpose of lower loss, however high mode birefringence and low relative absorption loss can not coexist in such a kind of fiber.

The Birefringence of the chalcogenide As-Ge-Se-S thin films by the electric field effects (전계효과에 의한 비정질 칼코게나이드 박막에서의 복굴절 특성)

  • Son, Chul-Ho;Jang, Sun-Joo;Yeo, Cheoi-Ho;Park, Jung-I1;Lee, Young-Jong;Chung, Hong-Bay
    • Proceedings of the KIEE Conference
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    • pp.1727-1729
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    • 2000
  • We has investigated the birefringence by the assisted electric field effect on $As_{40}Ge_{10}Se_{15}S_{35}$ thin films. Photoinduced birefringence has been studied in a chalcogenide material. We induced this thin films using linearly polarized He-Ne laser light(633nm) and detected polarized semiconductor laser light(780nm). To investigate the effect of electric field, various bias voltages applied. The result is shown that the birefringence has a higher value in +2V than others. We obtained the birefringence in the electric field effects by various voltages.

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A Study on Influence of Parameters and Characteristics in the Injection Process on the Birefringence and Refractive Index for Pickup Lens (Pickup 렌즈의 사출조건이 복굴절 및 굴절율에 미치는 영향에 관한 연구)

  • Lee, Seung-Joon;Hyun, Dong-Hoon
    • 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.

Finite-difference Time-domain Study on Birefringence Changes of the Axon During Neural Activation

  • Lee, Jong-Hwan;Kim, Sung-June
    • Journal of the Optical Society of Korea
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    • v.13 no.2
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    • pp.272-278
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    • 2009
  • Recently, there has been a growing interest in optical imaging of neural activity because the optical neuroimaging has considerable advantages over conventional imaging. Birefringence of the axon has been reported to change during neural activation, but the neurophysiological origin of the change is still unresolved. This study hypothesizes that the birefringence signal is at least partially attributed to the transient cellular volume change associated with nerve excitation. To examine this hypothesis, we investigated how the intensity of cross-polarized light transmitting through the axon would change as the size of the axon changes. For this purpose, a two-dimensional finite-difference time-domain program was developed with the improvement of the total-field/scattered-field method which reduces numerical noise. The results support our hypothesis in that the computed cross-polarized signals exhibit some agreement with previously-reported birefringence signals.