The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform
Patricia Blanco - One of the best experts on this subject based on the ideXlab platform.
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Simulation of imperfections in Plastic Lenses – transferring local refractive index changes into surface shape modifications
Advanced Optical Technologies, 2016Co-Authors: Josep Arasa, Carles Pizarro, Patricia BlancoAbstract:AbstractInjection molded Plastic Lenses have continuously improved their performance regarding optical quality and nowadays are as usual as glass Lenses in image forming devices. However, during the manufacturing process unavoidable fluctuations in material density occur, resulting in local changes in the distribution of refractive index, which degrade the imaging properties of the polymer Lens. Such material density fluctuations correlate to phase delays, which opens a path for their mapping. However, it is difficult to transfer the measured variations in refractive index into conventional optical simulation tool. Thus, we propose a method to convert the local variations in refractive index into local changes of one surface of the Lens, which can then be described as a free-form surface, easy to introduce in conventional simulation tools. The proposed method was tested on a commercial gradient index (GRIN) Lens for a set of six different object positions, using the MTF sagittal and tangential cuts to compare the differences between the real Lens and a Lens with homogenous refractive index, and the last surface converted into a free-form shape containing the internal refractive index changes. The same procedure was used to reproduce the local refractive index changes of an injected Plastic Lens with local index changes measured using an in-house built polariscopic arrangement, showing the capability of the method to provide successful results.
Wood-hi Cheng - One of the best experts on this subject based on the ideXlab platform.
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Lensed Plastic optical fiber with an aspherical fiber end formed by joining an aspherical Plastic Lens and a Plastic optical fiber using laser transmission welding
Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology, 2011Co-Authors: Yih-tun Tseng, Shu-ming Chang, Sheng-he Huang, Wood-hi ChengAbstract:Abstract In optical communication systems which require the coupling of the light source to the fiber, efficient coupling can be practically realized either using a separate Lens or by direct formation of the Lens at the fiber end. A novel Lensed Plastic optical fiber (LPOF) is presented with efficient coupling of the Plastic optical fibers with a light source. An aspherical Plastic Lens was bound with a flattened Plastic fiber end by laser transmission welding (LTW) to form an aspherical fiber endface which can provide better coupling efficiency than a spherical fiberface. An analysis demonstrates that LTW can offer strong welding with small heat affected zones that are appropriate for commercial use. In this study a useful method for manufacturing Lensed-end fibers is developed and demonstrated experimentally.
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Lensed Plastic Optical Fiber with a Convexo-Concave Fiber Endface for Coupling Laser Diodes With Plastic Optical Fiber
Journal of Manufacturing Science and Engineering-transactions of The Asme, 2011Co-Authors: Yih-tun Tseng, Shu-ming Chang, Sheng-he Huang, Wood-hi ChengAbstract:This work presents a novel Lensed Plastic optical fiber (POF), efficiently coupled with a light source. A convexo-concave Plastic Lens (CCPL) was bound to a flat-end Plastic optical fiber using laser transmission welding (LTW) to form a convexo-concave-shaped fiber endface (CCSFE). The novel Lensed Plastic optical fiber has a longer working distance and a higher coupling efficiency than conventional Lensed Plastic optical fibers. 850 nm fiber is often used in high-power 2.5 Gb/s transmission rate. Experimental POF is perfluorinated POF, 62.5–500 μm diameter, 850∼1300 μm wavelength, 10 dB/km power loss rate, 2.5 Gb/s transmission rate. Because of the small diameter of POF, it is difficult to couple between the light source and POF. Therefore, it is important to develop a Lensed fiber structure to increase the coupling efficiency. Experiments indicate that the coupling efficiency between a laser diode at a wavelength of 850 nm and a graded-index POF is as high as 85% with a long working distance of 250 μm. The measured tolerance, in relation to the lateral and vertical displacements and tilt, are satisfactory for practical active alignment.
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Lensed Plastic Optical Fiber with a Convexo-Concave Fiber Endface for Coupling Laser Diodes With Plastic Optical Fiber
Journal of Manufacturing Science and Engineering-transactions of The Asme, 2011Co-Authors: Yih-tun Tseng, Shu-ming Chang, Sheng-he Huang, Wood-hi ChengAbstract:This work presents a novel Lensed Plastic optical fiber (POF), efficiently coupled with a light source. A convexo-concave Plastic Lens (CCPL) was bound to a flat-end Plastic optical fiber using laser transmission welding (LTW) to form a convexo-concave-shaped fiber endface (CCSFE). The novel Lensed Plastic optical fiber has a longer working distance and a higher coupling efficiency than conventional Lensed Plastic optical fibers. 850 nm fiber is often used in high-power 2.5 Gb/s transmission rate. Experimental POF is perfluorinated POF, 62.5–500 μm diameter, 850∼1300 μm wavelength, 10 dB/km power loss rate, 2.5 Gb/s transmission rate. Because of the small diameter of POF, it is difficult to couple between the light source and POF. Therefore, it is important to develop a Lensed fiber structure to increase the coupling efficiency. Experiments indicate that the coupling efficiency between a laser diode at a wavelength of 850 nm and a graded-index POF is as high as 85% with a long working distance of 250 μm. The measured tolerance, in relation to the lateral and vertical displacements and tilt, are satisfactory for practical active alignment.
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Failure Mechanisms Associated With Lens Shape of High-Power LED Modules in Aging Test
IEEE Transactions on Electron Devices, 2008Co-Authors: Yi-cheng Hsu, Yu-kuan Lin, Ming-hung Chen, Chun-chin Tsai, Jao-hwa Kuang, Sheng-bang Huang, Wood-hi ChengAbstract:High-power light-emitting diode (LED) modules encapsulated with different Lens shapes after a thermal-aging test were studied experimentally and numerically. Samples from different manufacturers were aged at 80degC, 100degC, and 120degC under a constant driving voltage of 3.2 V. The results showed that the LED modules encapsulated with a hemispherical-shaped Plastic Lens exhibited a better lifetime due to better thermal dissipation than those with cylindrical-or elliptical-shaped Plastic Lenses. Results also showed that the optical power of the LED modules increased after removing the Plastic Lens because degradation of the Lens material decreased the amount of light. The key module package-related failure modes under thermal-aging were identified as the degradation of the Plastic Lens and Lens material. A finite-element method (FEM) simulation showed that thermal and major principle stress distributions of the high-power LED modules were dependent on aging temperature. Both experimental and FEM simulated results clearly indicated that a uniformly thermal dissipation to minimize the thermal effect along the thermal path from the LED chip to the Plastic Lens is essential to extend the operating life of high-power LED modules.
Josep Arasa - One of the best experts on this subject based on the ideXlab platform.
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Accurate polarimeter with multicapture fitting for Plastic Lens evaluation
Optical Engineering, 2016Co-Authors: Noemí Domínguez, Daniel Mayershofer, Cristina Batalla García, Josep ArasaAbstract:Due to their manufacturing process, Plastic injection molded Lenses do not achieve a constant density throughout their volume. This change of density introduces tensions in the material, inducing local birefringence, which in turn is translated into a variation of the ordinary and extraordinary refractive indices that can be expressed as a retardation phase plane using the Jones matrix notation. The detection and measurement of the value of the retardation of the phase plane are therefore very useful ways to evaluate the quality of Plastic Lenses. We introduce a polariscopic device to obtain two-dimensional maps of the tension distribution in the bulk of a Lens, based on detection of the local birefringence. In addition to a description of the device and the mathematical approach used, a set of initial measurements is presented that confirms the validity of the developed system for the testing of the uniformity of Plastic Lenses.
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Simulation of imperfections in Plastic Lenses – transferring local refractive index changes into surface shape modifications
Advanced Optical Technologies, 2016Co-Authors: Josep Arasa, Carles Pizarro, Patricia BlancoAbstract:AbstractInjection molded Plastic Lenses have continuously improved their performance regarding optical quality and nowadays are as usual as glass Lenses in image forming devices. However, during the manufacturing process unavoidable fluctuations in material density occur, resulting in local changes in the distribution of refractive index, which degrade the imaging properties of the polymer Lens. Such material density fluctuations correlate to phase delays, which opens a path for their mapping. However, it is difficult to transfer the measured variations in refractive index into conventional optical simulation tool. Thus, we propose a method to convert the local variations in refractive index into local changes of one surface of the Lens, which can then be described as a free-form surface, easy to introduce in conventional simulation tools. The proposed method was tested on a commercial gradient index (GRIN) Lens for a set of six different object positions, using the MTF sagittal and tangential cuts to compare the differences between the real Lens and a Lens with homogenous refractive index, and the last surface converted into a free-form shape containing the internal refractive index changes. The same procedure was used to reproduce the local refractive index changes of an injected Plastic Lens with local index changes measured using an in-house built polariscopic arrangement, showing the capability of the method to provide successful results.
Carles Pizarro - One of the best experts on this subject based on the ideXlab platform.
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Simulation of imperfections in Plastic Lenses – transferring local refractive index changes into surface shape modifications
Advanced Optical Technologies, 2016Co-Authors: Josep Arasa, Carles Pizarro, Patricia BlancoAbstract:AbstractInjection molded Plastic Lenses have continuously improved their performance regarding optical quality and nowadays are as usual as glass Lenses in image forming devices. However, during the manufacturing process unavoidable fluctuations in material density occur, resulting in local changes in the distribution of refractive index, which degrade the imaging properties of the polymer Lens. Such material density fluctuations correlate to phase delays, which opens a path for their mapping. However, it is difficult to transfer the measured variations in refractive index into conventional optical simulation tool. Thus, we propose a method to convert the local variations in refractive index into local changes of one surface of the Lens, which can then be described as a free-form surface, easy to introduce in conventional simulation tools. The proposed method was tested on a commercial gradient index (GRIN) Lens for a set of six different object positions, using the MTF sagittal and tangential cuts to compare the differences between the real Lens and a Lens with homogenous refractive index, and the last surface converted into a free-form shape containing the internal refractive index changes. The same procedure was used to reproduce the local refractive index changes of an injected Plastic Lens with local index changes measured using an in-house built polariscopic arrangement, showing the capability of the method to provide successful results.
Elsa Lacombe - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of silicon photonic technology for the development of innovative 40 Gbps wireless link above 200 GHz
2018Co-Authors: Elsa LacombeAbstract:With the booming of mobile data traffic, the need for higher data-rates is clearly felt. To cope with this strong demand and support the 5G roll-out, the capacity of the mobile communication network is being improved every day with many solutions, among which the development and installation of millimeterwave (mmW) wireless systems operating at up to 10 Gb/s. However, in order to deliver such high speeds to the user, the fronthaul/backhaul network sending data back to the core network would require above 40 Gb/s data-rate wireless links. This challenge generates a growing interest for sub-mmW and THz frequencies (0.1 THz – 1 THz) at which up-to 100 GHz bandwidth (BW) is accessible. In such BW, it would be possible to achieve up to 100 Gb/s data-rates while using simple modulation schemes to reduce the wireless system’s power consumption. Targeting mass-market high data-rates applications, Silicon Photonics technology seems very promising as it benefits from wide intrinsic BW and powerefficient components, as well as high integration levels and low manufacturing costs. In this context, a main aspect of this PhD project is the evaluation of an industrial Silicon Photonics technology for the development of a THz system-on-chip transmitter capable of reaching up to 100 Gb/s using a photodiode. Since THz antennas are also a hot topic for THz point-to-point transmission, a second aspect of this PhD study is the design of a low-cost and compact THz antenna-system. Hence, a planar antenna using low-loss organic packaging technology and a 3D-printed Plastic Lens were developed in order to assess those industrial prototyping techniques above 200 GHz.
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Low-cost Plastic Lens fabricated in FDM 3D-printing technology targeting high data rate wireless links above 200 GHz
2017 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2017Co-Authors: Elsa Lacombe, Frédéric Gianesello, Aimeric Bisognin, Cyril Luxey, Diane Titz, Heiko Gulan, Thomas Zwick, Jorge Costa, Carlos A. FernandesAbstract:With the booming of data traffic, operating frequencies of wireless systems are evolving towards the sub-THz spectrum in order to enhance the capacity of communication networks. Therefore, gain requirements of sub-THz antenna systems are crucial in order to allow satisfactory wireless data transfer. A good solution for improving the gain of integrated antennas consists in using a dielectric Lens. In this paper, a sub-THz Acrylonitrile Butadiene Styrene (ABS) Plastic Lens is proposed. Using additive manufacturing, low-cost and fast prototyping of the Lens was achieved. A gain improvement ranging from 12 dB to 19 dB in the broadside direction is measured from 200 GHz to 300 GHz which demonstrates great potential for sub-THz applications.
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Low-cost 3D-printed 240 GHz Plastic Lens fed by integrated antenna in organic substrate targeting sub-THz high data rate wireless links
2017 IEEE International Symposium on Antennas and Propagation & USNC URSI National Radio Science Meeting, 2017Co-Authors: Elsa Lacombe, Frédéric Gianesello, Aimeric Bisognin, Cyril Luxey, Diane Titz, Heiko Gulan, Thomas Zwick, Jorge R. Costa, Carlos A. FernandesAbstract:Millimeter-wave and sub-THz low-cost antenna systems are hot topics in order to increase data rates. At these frequencies, quasi-optical antennas are often required to increase achievable gains and therefore link range. At 60 GHz and up-to 140 GHz, low-cost ABS-Plastic Lenses fabricated in 3D printing technology were successfully demonstrated. In this paper, the same approach is presented in the 215–240 GHz band. For the first time, an integrated antenna in organic substrate is used as a feed in order to illuminate a 3D-printed ABS-Plastic Lens. A co-design between those two elements was performed, a gain increase of ∼11 dB is then achieved for a Lens diameter of 9 mm. A peak gain of 18 dBi has been measured at 235 GHz.