Introduction： The human optic nerve head （ONH） is vulnerable to the damage in glaucomatous high intraocular pressure （IOP）. In order to analyze the human ONH head stress and deformation in high IOP, an in vivo th...Introduction： The human optic nerve head （ONH） is vulnerable to the damage in glaucomatous high intraocular pressure （IOP）. In order to analyze the human ONH head stress and deformation in high IOP, an in vivo three-dimensional （3D） ONH model was reconstructed by optical coherence tomography （OCT） images and magnetic resonance imaging （MRI） images. Materials and Methods： A human eye was scanned by MRI and OCT in serial imaging protocol. The sclera and ONH were segmented from the images, and 3D models were reconstructed by multimodality image registration. Through the morphological segmentation, part of lamina cribrosa （LC） was acquired and reconstructed in combination with the ONH and sclera. Results： The models of ONH and sclera were got, the part of LC was included in the model. In the analysis of FEM, the ONH was compressed and the cup/disk ratio was changed obviously in high glaucomatous IOP. Discussion： This study described a method to build a 3D in vivo ONH model by image processing. It can be used in biomechanieal analysis, and provide the stress state of ONH for the research about the fundus damage of glaucoma.展开更多
The muhimode interference （MMI） couplers, which operate at 1. 55 microns in deep rib InGaAsP/InP waveguide with large lateral confinement and tunable power splitting ratios, are of high interest in integrated optics...The muhimode interference （MMI） couplers, which operate at 1. 55 microns in deep rib InGaAsP/InP waveguide with large lateral confinement and tunable power splitting ratios, are of high interest in integrated optics. The gold contacts are applied on the top of waveguides where tuning is desired and the plasma effect will lead to negative refractive index change. The three-dimensional （3D） finite difference beam propagation method（FD-BPM） is used to model the tunable MMI couplers. The length of a 2 × 2 overlap-MMI is determined by FD-BPM, so the longitudinal position of tuning spots is obtained. The position of gold contacts with two types, the edge-pads or center-pad, are also determined. In our design, the length of MMI is 180 microns. If the width of pads is 50 microns and the refractive index is tuned from 0 to -0. 027, the power ratio is tuned from 50 ： 50 to the maximum 88.5 ： 11.4. For deep rib structure, the effective index（EI） method can not be used to simplify the 3D waveguide to plane waveguide because of its lower precision, and so the direct 3D FD-BPM simulation is necessary for the design of 3D MMI couplers.展开更多
基金National Natural Science Foundation of Chinagrant number: 31070840 and 11102123+3 种基金Funding Project for Academic Human Resources Development in Institutions of Higher Learning Under the Jurisdiction of Beijing Municipalitygrant number: PHR201110506General Program of Science and Technology Development Project of Beijing Municipal Education Commissiongrant number: KM201110025009
文摘Introduction： The human optic nerve head （ONH） is vulnerable to the damage in glaucomatous high intraocular pressure （IOP）. In order to analyze the human ONH head stress and deformation in high IOP, an in vivo three-dimensional （3D） ONH model was reconstructed by optical coherence tomography （OCT） images and magnetic resonance imaging （MRI） images. Materials and Methods： A human eye was scanned by MRI and OCT in serial imaging protocol. The sclera and ONH were segmented from the images, and 3D models were reconstructed by multimodality image registration. Through the morphological segmentation, part of lamina cribrosa （LC） was acquired and reconstructed in combination with the ONH and sclera. Results： The models of ONH and sclera were got, the part of LC was included in the model. In the analysis of FEM, the ONH was compressed and the cup/disk ratio was changed obviously in high glaucomatous IOP. Discussion： This study described a method to build a 3D in vivo ONH model by image processing. It can be used in biomechanieal analysis, and provide the stress state of ONH for the research about the fundus damage of glaucoma.
文摘The muhimode interference （MMI） couplers, which operate at 1. 55 microns in deep rib InGaAsP/InP waveguide with large lateral confinement and tunable power splitting ratios, are of high interest in integrated optics. The gold contacts are applied on the top of waveguides where tuning is desired and the plasma effect will lead to negative refractive index change. The three-dimensional （3D） finite difference beam propagation method（FD-BPM） is used to model the tunable MMI couplers. The length of a 2 × 2 overlap-MMI is determined by FD-BPM, so the longitudinal position of tuning spots is obtained. The position of gold contacts with two types, the edge-pads or center-pad, are also determined. In our design, the length of MMI is 180 microns. If the width of pads is 50 microns and the refractive index is tuned from 0 to -0. 027, the power ratio is tuned from 50 ： 50 to the maximum 88.5 ： 11.4. For deep rib structure, the effective index（EI） method can not be used to simplify the 3D waveguide to plane waveguide because of its lower precision, and so the direct 3D FD-BPM simulation is necessary for the design of 3D MMI couplers.
