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Glaucoma is an ophthalmic disease which is among the chief causes of visual impairment across the globe. The clarity of the optic disc (OD) is crucial for recognizing glaucoma. Since existing methods are unable to successfully integrate multi-view information derived from shape and appearance to precisely explain OD for segmentation, this paper proposes a saliency-based level set with an enhanced active contour method (SL-EACM), a modified locally statistical active contour model, and entropy-based optical disc localization. The significant contributions are that i) the SL-EACM is introduced to address the often noticed problem of intensity inhomogeneity brought on by defects in imaging equipment or fluctuations in lighting; ii) to prevent the integrity of the OD structures from being compromised by pathological alterations and artery blockage, local image probability data is included from a multi-dimensional feature space around the region of interest in the model; and iii) the model incorporates prior shape information into the technique, for enhancing the accuracy in identifying the OD structures from surrounding regions. Public databases such as CHASE_DB, DRIONS-DB, and Drishti-GS are used to evaluate the proposed model. The findings from numerous trials demonstrate that the proposed model outperforms state-of-the-art approaches in terms of qualitative and quantitative outcomes.

Silicon-based optical media present several desirable properties for a wide range of applications. Herein, we propose a novel hybrid integration scheme that combines a silicon photonics platform and a 5.5%--silica planar-lightwave circuit (PLC) platform. By exploiting the performance advantages of each platform, we fabricated a polarization-insensitive low-crosstalk 8 8 silicon photonics switch butt-jointed with a compact 5.5%--silica PLC-based 100-GHz 8-channel arrayed waveguide grating (AWG). The device was driven by a smartphone-sized (9 cm 13.5 cm) control board. The fabricated device exhibits a fiber-to-fiber insertion loss of 12.6 dB, an average polarization-dependent loss of less than 0.57 dB, and less than -40 dB leakage to non-target output ports. We also demonstrate two uses of the proposed device. The first is the DEMUX and Switch operation, in which the spectrally divided light by the AWG is routed to an arbitrary output port by a subsequent switch. The second is the Switch and MUX operation, in which arbitrary wavelengths from arbitrary input ports are merged by the AWG. No spectral degradation was observed in either operation. These results demonstrate the potential of the 5.5%--PLC/silicon photonics hybrid platform for compact, low-power, and fast-switching applications.

Galactic bars are important drivers of galactic evolution, and yet how they impact the interstellar medium and correspondingly star formation, remains unclear. We present simulation results for two barred galaxies with different formation mechanisms, bars formed in isolation or via a tidal interaction, to consider the spatially and temporally varying trends of star formation. We focus on the early (< 1Gyr) epoch of bar formation so that the interaction is clearly identifiable. The nearby NGC 4303 (isolated) and NGC 3627 (interaction history) are selected as observational analogues to tailor these simulations. Regardless of formation mechanism, both models show similar internal dynamical features, although the interaction appears to promote bar-arm disconnection in the outer disc velocity structure. Both bars trigger similar boosts in star formation (79%; 66%), while the interaction also triggers an earlier 31% burst. Significant morphological dependence is observed in the relation between surface gas and star formation rate. In both cases, the bar component is notably steepest; the arm is similar to the overall disc average; and the inter-arm clearly the shallowest. A distinguishable feature of the tidal disc is the presence of moderately dense, inefficiently star forming gas mostly confined to tidal debris outside the optical disc. The tidal disc also exhibits a unique trend of radially increasing star formation efficiency and a clear dearth of star formation which persists along the bar between the centre and bar ends. These are potential signatures for identifying a barred system post-interaction., 19 pages, 15 figures, accepted for publication in MNRAS

O glaucoma é uma neuropatia óptica cuja progressão pode levar a cegueira. Representa a principal causa de perda visual de caráter irreversível em todo o mundo para homens e mulheres. A detecção precoce através de programas de rastreamento feita por especialistas é baseada nas características do nervo óptico, em biomarcadores oftalmológicos (destacando-se a pressão ocular) e exames subsidiários, com destaque ao campo visual e OCT. Após o reconhecimento dos casos é feito o tratamento com finalidade de estacionar a progressão da doença e melhorar a qualidade de vida dos pacientes. Contudo, estes programas têm limitações, principalmente em locais mais distantes dos grandes centros de tratamento especializado, insuficiência de equipamentos básicos e pessoal especializado para oferecer o rastreamento a toda a população, faltam meios para locomoção a estes centros, desinformação e desconhecimento da doença, além de características de progressão assintomática da doença. Esta tese aborda soluções inovadoras que podem contribuir para a automação do rastreamento do glaucoma utilizando aparelhos portáteis e mais baratos, considerando as necessidades reais dos clínicos durante o rastreamento. Para isso foram realizadas revisões sistemáticas sobre os métodos e equipamentos para apoio à triagem automática do glaucoma e os métodos de aprendizado profundo para a segmentação e classificação aplicáveis. Também foi feito um levantamento de questões médicas relativas à triagem do glaucoma e associá-las ao campo da inteligência artificial, para dar mais sentido as metodologias automatizadas. Além disso, foi criado um banco de dados privado, com vídeos e imagens de retina adquiridos por um smartphone acoplado a lente de baixo custo para o rastreamento do glaucoma e avaliado com métodos do estado da arte. Foram avaliados e analisados métodos de detecção automática de glaucoma utilizando métodos de aprendizado profundo de segmentação do disco e do copo óptico em banco de dados públicos de imagens de retina. Finalmente, foram avaliadas técnicas de mosaico e de detecção da cabeça do nervo óptico em imagens de baixa qualidade obtidas para pré-processamento de imagens adquiridas por smartphones acoplados a lente de baixo custo. Glaucoma is an optic neuropathy whose progression can lead to blindness. It represents the leading cause of irreversible visual loss worldwide for men and women. Early detection through screening programs carried out by specialists is based on the characteristics of the optic papilla, ophthalmic biomarkers (especially eye pressure), and subsidiary exams, emphasizing the visual field and optical coherence tomography (OCT). After recognizing the cases, the treatment is carried out to stop the progression of the disease and improve the quality of patients’ life. However, these screening programs have limitations, particularly in places further away from the sizeable, specialized treatment centers, due to the lack of essential equipment and technical personnel to offer screening to the entire population, due to the lack of means of transport to these centers, due to lack of information and lack of knowledge about the disease, considering the characteristics of asymptomatic progression of the disease. This thesis aims to develop innovative approaches to contribute to the automation of glaucoma screening using portable and cheaper devices, considering the real needs of clinicians during screening. For this, systematic reviews were carried out on the methods and equipment to support automatic glaucoma screening, and the applicable deep learning methods for segmentation and classification. A survey of medical issues related to glaucoma screening was carried out and associated with the field of artificial intelligence to make automated methodologies more effective. In addition, a private dataset was created, with videos and retina images acquired using a low-cost lens-coupled cell phone, for glaucoma screening and evaluated with state-of-the-art methods. Methods of automatic detection of glaucoma using deep learning methods of segmentation of the disc and optic cup were evaluated and analyzed in a public database of retinal images. In the case of deep learning classification methods, these were evaluated in public databases of retina images and in a private database with low-cost images. Finally, mosaic and object detection techniques were evaluated in low-quality images obtained for pre-processing images acquired by cell phones coupled with low-cost lenses.

The optical matrix formalism is applied to find optical parameters such as focal distance, back and front focal points, principal planes and the object image equation for a thick spherical lens immerse in two optical media of different indexes of refraction. Then, the formalism is applied to systems compound of two, three and N thick lenses in cascade, immersed in three, four and N+1 optical media of different indexes, respectively. It is found that a simple Gaussian equation is enough to relate object and image distances no matter the number of lenses. This formalism is validated trough a simple optical matrix model of the human eye.

The paper proposes a method for finding the characteristics of the birefringence in optical media that possess several types of anisotropy simultaneously. It is proposed to characterize birefringence by a vector equal to the Stokes vector of the eigenpolarization multiplied by the phase shift between waves with eigenpolarizations. It is shown that such a vector of the complex birefringence is equal to the sum of such vectors corresponding to the component birefringences. The proposed method is well compatible with approaches to finding the polarization dynamics of propagating radiation based on the concepts of the Jones matrix and the Poincare sphere.

Glaucoma is one of the leading causes of blindness for people over the age of 60. For the automatic glaucoma detection using fundus images, several approaches have been recently developed. However, the extraction of optic cup boundary considered as critical work due to the blood vessels interweavement and also the significant challenges in accurate localization of affected optical disc based on size of the cup which is either too small or large. To overcome this challenges efficient technique needs to be considered. To accurately detect the glaucoma and correspondingly the optic cup OC and optic disk OD boundary the ensemble based CNN classification with spatially based ellipse fitting curve model (SBEFCM) has been proposed. In this study, the glaucoma or diabetes retinopathy DR classification has been performed by the ensemble CNN classification. The optic disc and optic cup boundary detected by new spatially weighted ellipse fitting model SBEFCM. For the proposed SBEFCM, which enhances and prolongs the multi-ellipse fitting technique. The ensemble based CNN classification is performed for various datasets such as LAG, RIM-ONE and local retinal glaucoma dataset. Previously the input fundus image is pre-processed and further blood vessel segmentation performed to avoid the interweavement with surrounding tissues and blood vessels. The new SBEFCM accurately detected the ratio of OC and OD boundary prediction which are depicted and by using the ensemble CNN classification, various performance metrics such as sensitivity, specificity, accuracy and AUC values has been identified for glaucoma detection and by comparison the proposed ensemble CNN outperforms the existing methods.

To increase the recording density of optical discs, analog recording techniques such as the use of orthogonal frequency division multiplexing (OFDM) method has been investigated. In OFDM method, the recording signal is separated into several sub frequency bands. So the readout channel becomes tolerant of the deterioration by disturbances such as defocus and disc skew in optical disc systems. Faster than Nyquist (FTN) signaling is known as the method to increase the transfer rate of OFDM channels in the area of telecommunication. In this paper, a possibility to achieve higher recording density of optical disc systems by applying the FTN is described. The readout signal of FTN-OFDM method was calculated using the optical disc readout and the signal processing models considering the crosstalk from adjacent tracks and FTN applied to a five-channel 64-QAM OFDM system. The calculation results show that the proposed system has a possibility of 1.5 times recording density of the conventional optical disc with a similar tolerance to disturbances.

Introduction. Recent population studies reveal steady growth in intraocular lens (IOL) exchanges including those for refractive and other optical reasons. To lower complication risks related to IOL exchange, we introduced a modular IOL model with replaceable optical part.Purpose: preliminary analysis of modular IOL implantation clinical results.Patients and methods. From August 2018 to February 2020, five patients as part of their surgical treatment for various forms of cataract received newly designed modular IOLs. The modular IOL is composed of two separate parts — haptic and optic, manufactured from the same elastic acrylic material with hydrophobic properties. The haptic includes a closed ring and a pair of open equally distant loops in a unified design. The haptic ring with projections serves as a base for optical disk. The current study evaluated characteristics of the IOL implantation and assembly process, as well as possible development of intra- and early postoperative complications.Results. First implantations of the modular IOL accomplished using standard surgical instrumentation and disposables passed without complications. We did not observe scratches, breaks or any other mechanical damage to neither haptic, nor optical parts. During simultaneous implantation, optical disks fixated in haptic rings preserved their due positioning after transiting through slender injector channel. There were no specific, modular-IOL related complications in the early postoperative period. The optical disk maintained correct location, delimited by fixation leaflets of the haptic ring.Conclusion. Early results for clinical application of the novel modular IOL demonstrated feasibility of its safe implantation in disassembled and preassembled modes.

The generation of high-intensity optical fields from harmonic-wave photons, interacting via a cross-phase modulation with dark solitons both propagating in a Kerr nonlinear medium, is examined. The focus is on a pump consisting of time-entangled dark-soliton patterns, forming a periodic waveguide along the path of the harmonic-wave probe. It is shown that an increase of the strength of cross-phase modulation respective to the self-phase modulation, favors soliton-mode proliferation in the bound-state spectrum of the trapped harmonic-wave probe. The induced soliton modes, which display the structures of periodic soliton lattices, are not just rich in numbers, they also form a great diversity of population of soliton crystals with a high degree of degeneracy., 9 pages, 3 figures, 3 tables, submitted

Morning Glory Syndrome (MGS) is an uncommon congenital anomaly of the eye nerve (optic nerve) that resembles a flower known as morning glory, impairs vision, and may be associated with both ocular and non-ocular abnormalities. It has a characteristic fundoscopic appearance consisting of a large funnel-shaped cavity on the optical disc.We register an unusual congenital anomaly of the optic disc in a three-year-old female child., Синдромот на “Morning Glory” (MGS -Morning Glory Syndrom) е невообичаена конгенитална аномалија на oптичкиот нерв кој наликува на цвет познат како „morning glory“, го нарушува видот и може да бидe поврзан и со окуларни и неокуларни абнормалности. Има карактеристичен фундоскопски изглед кој се состои од големa празнина во форма на инка на оптичкиот диск. Во овој труд презентираме невообичаена вродена аномалија на оптичкиот диск кај три годишно дете од женскиот пол.

The object of study is a cement composite material with powdered utilized optical discs. The objective is to establish the dependences of the main strength characteristics – com-pressive strength, bending strength, and density – on the amount of waste added into the mix-ture and the water-cement ratio.The compositions of the mixtures for the production of the cement composite material samples consisted of the following components: cement, sand, powdered waste in the form of utilized optical discs and water.Based on the results of testing the samples, mathematical models have been developed which describe the dependences of the physical and mechanical properties of the cement com-posite material samples on the fraction of waste and water-cement ratio. It was found that with an increase in the amount of powdered waste added into the mixture, it reduces the compressive strength, bending strength, and density of the samples under study, however, the optimization of the water-cement ratio makes it possible to obtain equal strength compositions with a differ-ent fraction of waste.Component compositions of cement composite material mixtures with the addition of powdered utilized optical discs in the amount of 10 to 25 % of the total filler mass, which can provide construction products with a compressive strength class B20, are presented.

With the development of ultra-high-density optical storage technology, the density of storage media is getting higher and higher, but the increase of the capacity of the optical disk leads to the reduce of the lens-disk interface gap and the tolerance of the focus error dramatically. In the case of extremely small spacing, various external disturbances are highly likely to cause a collision between the optical lens and the disc. In order to avoid the collision between the optical lens and disk, effectively eliminate the deterministic disturbance and suppress the unknown random disturbance, in this paper a multi-objective optimal output feedback controller design approach is proposed within the Q (Youla)-parameterized regulator scheme. The optimal Q parameter in the controller is obtained by solving the properly formulated linear matrix inequalities (LMIs). The experimental results show that the designed Q-parameterized controller can eliminate the influence of various disturbances and suppress the occurrence of collisions effectively.

The operating system is a collection of programes (algorithms) designed to manage all the comp uter system resources, such as processors, main storage and secondary storage, and input/output devices. Optical and magnetic disks are the most common secondary storage devices. The work described in this paper is mainly directed to the optical disk. Different optical disk storage technologies are discussed in terms of information about physical disk storage, file systems and access methods. Comparisons are also made between magnetic and optical disk storages.

Defocus detection technology is the key technology in the fields of laser direct writing, optical disc storage, and high-precision lithography, which directly affects the accuracy of line drawing. In this paper, using the principle of astigmatic method, combined with differential technology, a nano-level defocus detection method based on differential astigmatism for the high numerical aperture systems is proposed. Firstly, by establishing a mathematical model, the theoretical analysis and simulation of the defocus detection method based on differential astigmatism are carried out. In addition, the system parameters at the maximum sensitivity of the high numerical aperture defocus detection system is also solved. Secondly, the defocus detection experimental system based on astigmatic method was built for experimental demonstration. Finally, using the objective lens with a numerical aperture of 0.8, the focus error signal curve with a good linear relationship is obtained in this paper. The linear range is 6μm; the system sensitivity can reach 5 nm; the system detection accuracy is 30 nm, and the repeat positioning accuracy can reach 30 nm. The defocus detection method based on the high numerical aperture objective lens has the advantages of large detection range, high detection accuracy and compact system structure, which can be widely used in various new high-precision laser processing fields.

The original mathematical treatment used in the analysis of the Fizeau experiment of 1851, which measured the relative speed of light in a moving medium, assumes that light travels through the water in a smooth continuous flow, at a speed less than the speed of light in a vacuum (relative to the water). Thus, it assumes that the water’s velocity vector can simply be added to that of the light. However, light is transmitted through optical media, such as water, by a continuous process of charge excitation (semi-absorption) and re-emission by the water molecules; but travels between them at the full speed of light (in a vacuum). Thus, the mathematics describing the process of Fresnel dragging must be formulated differently and can then be explained by classical physics, allowing the entire process to be fully visualized.

The optical pickup unit (OPU) is an optical assembly, which is used for reading and writing digital optical disks. It consists of a laser diode, quadrant photodetector, and other optical components to maintain focus. This arrangement of the laser and photodetector is very similar to those in expensive equipment, such as atomic force microscopes, used for nanoscale metrology. Many researchers have hence investigated the use of an OPU to design low-cost alternatives. However, these nonstandard uses of an OPU are challenging since the OPU has originally been optimized to sense reflections from the highly reflecting surface of an optical disk. In this work, we present a new synchronous detection-based method that improves the performance of the OPU in measuring the reflection from poorly reflecting substrates. This method utilizes the high bandwidth of both the laser and photodetector of the OPU. We excite the laser with a pulsed input and look for a signal at the pulsing frequency in the output from the OPU. This signal is further processed through a phase-sensitive detector. We show that this method reduces the offsets in the measurement and allows us to make effective use of a higher gain to measure the reflection from substrates with poor reflectivity.

Proportional-integral-derivative (PID) control is commonly used in industrial automatic control systems. However, it is not straightforward to determine control gains in a PID controller for satisfactory closed-loop performance. Many research works have been devoted to the auto-tuning of PID control gains. In contrast to previous studies, this paper develops an auto-tuning rule for PID controllers to simultaneously satisfy specifications of both steady-state error and relative stability, in which stability is specified in terms of phase margin. To illustrate the proposed auto-tuning rule, a focus servo of an optical disk drive is used, in which a voice coil motor drives a lens to focus a laser beam on a data layer of an optical disk. Experimental results show the effectiveness of the proposed PID auto-tuning process.