The problem of using a computer to control the figuring of an optical surface is investigated. By assuming a linear, shift invariant figuring process, the amount of material removed during each figuring run can be computed. This is done by convolving a tool removal profile with a dwell function that describes the amount of time the figuring tool spends in each area element on the surface. Four methods of computing a dwell function that will best remove the figure errors are described. The advantages of making surface figure measurements using direct wavefront measurement techniques over the interferogram analysis methods used in previous computer controlled figuring machines are also discussed. The design and construction of a computer controlled optical figuring machine is then reviewed. The machine uses a computer controlled heterodyne interferometer to provide optical testing data on the surface being polished. Two microcomputers are used to analyze the test data and run the machine. Optical figuring is performed by scanning a polishing head with a known removal function over the surface at a rate derived from the surface errors. The operation of the software that computes the run path data and controls the machine hardware is outlined. The performance of each of the machine components is evaluated by comparing the behavior predicted by theory to the measured behavior. Initially, the accuracy of the interferometer is measured. The interferometer is then used to determine the performance of the polishing head by measuring the tool removal function. It is then shown that the machine can be run so that a predictable amount of material is removed from the surface. Finally, the feedback loop is closed and surface figure data from the interferometer is used to correctly polish the central region of a 16 inch diameter mirror. It is shown that the surface figure can be predicted with good accuracy over the entire surface. This work concludes with recommendations for improving the machine hardware and for improving the figuring performance near the edge of the surface being polished.

Cataract is a condition in the eye that if left untreated, could lead to blindness. One of the effective ways to treat cataract is the removal of the cataractous natural crystalline lens and implantation of an artificial lens called an intraocular lens(IOL). The designs of the IOLs have shown improvements over the years to further imitate natural human vision. A need for an objective testing and analysis tool for the latest IOLs grow with the advancements of the IOLs.In this dissertation, I present a system capable of objective test and analysis of the advanced IOLs. The system consists of-Model eye into which an IOL can be inserted to mimic conditions of the human eye.-Modulation Transfer Function measurement setup capable of through-focus test for depth of field studies and polychromatic test for study of effects of chromatization.-Use of Defocus Transfer Function to simulate depth of field characteristic of rotationally symmetric multifocal designs and extension of the function to polychromatic conditions.-Several target imaging experiments for comparison of stray light artifacts and simulation using a non-sequential ray trace package.

The Point Spread Function (PSF) indirectly encodes the wavefront aberrations of an optical system and therefore is a metric of the system performance. Analysis of the PSF properties is useful in the case of diffractive optics where the wavefront emerging from the exit pupil is not necessarily continuous and consequently not well represented by traditional wavefront error descriptors such as Zernike polynomials. The discontinuities in the wavefront from diffractive optics occur in cases where step heights in the element are not multiples of the illumination wavelength. Examples include binary or N-step structures, multifocal elements where two or more foci are intentionally created or cases where other wavelengths besides the design wavelength are used. Here, a technique for expanding the electric field amplitude of the PSF into a series of orthogonal functions is explored. The expansion coefficients provide insight into the diffraction efficiency and aberration content of diffractive optical elements. Furthermore, this technique is more broadly applicable to elements with a finite number of diffractive zones, as well as decentered patterns.

Purpose: To evaluate the incidence of central hole-induced ring-shaped dysphotopsia after posterior chamber phakic implantable collamer lens (ICL) with central hole (hole ICL) implantation and to investigate the causes of central hole-induced dysphotopsia. MethodsThe clinical study enrolled 29 eyes of 15 consecutive myopic patients implanted with hole ICL. The incidence of ring-shaped dysphotopsia after hole ICL implantation was evaluated. In the experimental simulation study, non-sequential ray tracing was used to construct myopic human eye models with hole ICL and ICL without a central hole (conventional ICL). Simulated retinal images measured in log-scale irradiance were compared between the two ICLs for an extended Lambertian light-emitting disc object 20cm in diameter placed 2m from the corneal vertex. To investigate the causes of hole-induced dysphotopsia, a series of retinal images were simulated using point sources at infinity with well-defined field angles (0 to -20 degrees) and multiple ICL models. ResultsOf 29 eyes, 15 experienced ring-shaped dysphotopsia after hole ICL implantation. The simulation study using an extended Lambertian source showed that hole ICL-evoked ring-shaped dysphotopsia was formed at a retinal field angle of 40 degrees. Component-level analysis using a well-defined off-axis point source from infinity revealed that ring-shaped dysphotopsia was generated by stray light refraction from the inner wall of the hole and the posterior ICL surface. ConclusionHole ICL-evoked ring-shaped dysphotopsia was related to light refraction at the central hole structure. Surgeons are advised to explain to patients the possibility of ring-shaped dysphotopsia after hole ICL implantation.

QC 351 A7 no. 75 / In the first part of this report the class of two-surface optical systems designated as modules, which have zero third-order spherical aberration relative to a pair of conjugate planes one of which is at infinity, has been further analyzed using the parameters of the Delano y,ÿ diagram. For a given set of three indices of refraction n1, n2, and n3, functional relationships among the y,j7 diagram parameters that eliminate simultaneously other Seidel aberrations are derived. Expressions for zero coma, astigmatism, and Petzval curvature are also given. Criteria for selecting the non - optical parameter k, which defines the desired properties of modules, are described. A one -to-one correspondence between the canonical optical parameters defined in previous studies of modules and certain quantities derivable from the y,ÿ diagram representation is shown. Critical values of the free parameters of modules for both the real and the imaginary cases are derived and defined relative to the y,,y diagram parameters. In the second part of this report an analysis is made of a class of modules referred to as the imaginary -case family depending on the new parameter 0. The critical values 00, 0_, and 0 *, which correspond to those obtained for real-case modules, are defined, and the conditions for their existence in the domain of are derived. These critical values, whose counterparts in the real case exist for both refracting and reflecting systems, do not exist for refracting imaginary-case modules when the indices of refraction are restricted to commonly available optical glasses. The critical values of 0 exist and have fixed values for all reflecting module systems. A method is proposed for classifying imaginary-case modules, which would permit comparison for coupling purposes.

QC 351 A7 no. 77 / Because of their light weight and low cost, transparent plastics would seem to be good materials for optical components. This thesis deals primarily with the feasibility of producing large ( >4 -in. -diam) plastic components of moderate precision (surface accuracies 1 fringe per inch of diameter). The structure and the physical and optical properties of plastics are discussed, with emphasis on their advantages and limitations for optical use. A series of experiments on grinding and polishing of plastics was conducted. Data are presented on grinding rates. Several polishing processes were evaluated, and a polishing technique for plastics was developed. Polishing rate data and surface roughness data are presented for several polishing processes. With proper techniques, we estimate that accuracies of about one fringe per inch are obtainable. A series of experiments was conducted on a process called compression forming, in which heat and pressure are applied to machined preforms in an attempt to obtain precision optical surfaces. The process is described in detail, and experimental results are discussed. Based on experimental results, improved processing conditions are suggested. Further experiments would be required to determine the ultimate process capability.

Objetivo: Determinar se o implante de uma determinada lente intraocular asférica resulta em redução das aberrações oculares e melhora da qualidade ótica e sensibilidade ao contraste sem que ocorra redução critica da profundidade de foco. Desenho: Estudo prospectivo, duplo-cego, randomizado. Métodos: Este estudo que incluiu 25 pacientes com catarata bilateral, uma LIO asférica foi implantada em um olho e uma LIO esférica no olho contralateral. Aberrações de maior ordem e parâmetros de qualidade ótica foram obtidos através de aberrômetro de retinoscopia dinâmica, 1 e 3 meses apos a cirurgia. Foi também medido a acuidade visual com e sem correção e a sensibilidade ao contraste. Acuidade visual para perto e distancia intermediaria foi obtida como forma de medida da profundidade de foco. Resultados: Não houve diferença estatisticamente significativa entre os grupos para acuidade visual corrigida e não corrigida 1 e 3 meses apos a cirurgia. Houve diferença estatisticamente significativa entre os grupos quanto a sensibilidade ao contraste sob condições fotópticas na frequência espacial de 12 ciclos por grau e sob condições mesópicas em todas as frequências espaciais estudadas. O grupo com a LIO Akreos AO obteve menores valores de aberrações de maior ordem totais e de aberração esférica com pupilas de 5 e 6 mm e melhores valores de qualidade ótica comparado ao grupo com LIO Akreos Fit (p <0.05). Não houve diferença significativa entre os grupos quando se investigou visão de perto e intermediaria corrigido para longe. Conclusões: A LIO asférica Akreos AO induziu menos aberrações de maior ordem além de produzir melhores parâmetros de qualidade ótica com melhores resultados de sensibilidade ao contraste em condições mesópicas sem redução critica de profundidade de foco quando comparado a LIO esférica Akreos Fit. / PURPOSE: To determine whether implantation of an aspherical intraocular lens (IOL) results in reduced ocular aberrations and improved optical quality and contrast sensitivity after cataract surgery without critical reduction of depth of focus. DESIGN: Double-blinded, randomized, prospective study. METHODS: In an intraindividual study of 25 patients with bilateral cataract, an aspherical IOL (Akreos Advanced Optic [AO]; Bausch & Lomb, Inc., Rochester, New York, USA) was implanted in one eye and a spherical IOL (Akreos Fit; Bausch & Lomb, Inc) in the fellow eye. Higher-order aberrations with a 5- and 6-mm pupil and optical quality parameters were measured with a dynamic retinoscopy aberrometer at 1 and 3 months after surgery. Uncorrected and best-corrected visual acuity and contrast sensitivity under mesopic and photopic conditions also were measured. Distancecorrected near and intermediate visual acuity were studied as a measurement of depth of focus. RESULTS: There was no statistically significant difference between eyes in uncorrected and best-corrected visual acuity at 1 and 3 months after surgery. There was a statistically significant between-group difference in contrast sensitivity under photopic conditions at 12 cycles per degree and under mesopic conditions at all spatial frequencies. The Akreos AO group obtained statistically significant lower values of higher-order aberrations and spherical aberration with 5- and 6-mm pupils and better optical quality parameters compared with the Akreos Fit group (P < .05). There was no significant difference in distance-corrected near and intermediate visual acuity between both groups. CONCLUSIONS: Aspherical aberration-free Akreos AO IOL induced significantly less higher-order aberrations and spherical aberration than the Akreos Fit. Contrast sensitivity under mesopic conditions and optical quality parameters were better with the Akreos AO with similar results of depth of focus.

Orientador: Patrícia Petromilli Nordi Sasso Garcia / Resumo: Este trabalho teve como objetivo observar o efeito da magnificação na postura de trabalho durante a realização de procedimentos odontológicos. Para isso, propôs-se a realização de sete estudos. Os estudos 1 e 2 tiveram como objetivo revisar a literatura para reunir informações disponíveis em torno da magnificação e ergonomia e da magnificação em endodontia, respectivamente. No estudo 3, foi realizada a observação da acuidade visual de estudantes de odontologia (N=160) em função de cinco diferentes condições visuais (olho nu, visão com lupa simples, visão com lupa do sistema Galilean, visão com lupa do sistema Keplerian e microscópio operatório) e em duas distâncias de trabalho (de 35cm boca/olhos e confortável para o operador). Além disso, os desvios angulares de pescoço foram registrados por meio de tomadas fotográficas. A acuidade visual foi medida através de uma tabela de E-optótipos localizados em cavidades Classe I de molares superiores. O desvio angular foi mensurado por meio do Software de Análise Postural. Realizou-se análise estatística descritiva e Análise de Variância - ANOVA a qual foi conduzida de forma independente para os diferentes anos do curso (2°, 3°, 4° e 5°). O nível de significância adotado para tomada de decisão foi de 5%. Observou-se interação significativa para o sistema de magnificação e distância (p<0,05) em todos os anos, tanto para a acuidade visual quanto para o ângulo de pescoço. Para a distância padronizada e em todos os anos do curso, a maior ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study aimed to observe the magnification effect on work posture during dental procedures. For this, seven studies were conducted. The studies 1 and 2 aimed to review the literature in order to gather informations regarding to magnification and ergonomics and magnification in endodontics, respectively. Study 3 aimed to determine dental students' visual acuity and neck angulation when using magnification devices and distances from the operating field. Forty students from each of the second through fifth years of the five-year program at the School of Dentistry of Araraquara were selected (N=160). Visual acuity was tested using a miniature Snellen eye chart under five different settings (unaided vision; simple loupe; Galilean loupe; Keplerian loupe and an operating microscope). Photographs were taken during the visual acuity exam in order to evaluate the angulation of the subjects' necks in a neutral posture. The two-factor Analysis of Variance - ANOVA and the Games-Howell post-hoc test were performed for the different years of the course (α=0.05). A significant difference in visual acuity and neck angulation was found between the "magnification device" and "distance" factors in each of the graduating classes analyzed (p<0.05). At a standardized distance, the Keplerian loupe, the Galilean loupe and the operating microscope provided the greatest visual acuity. At a subjectively comfortable distance, the Keplerian and Galilean loupes produced the best visual acuity. Regarding... (Complete abstract click electronic access below) / Doutor

A reflective Tiered Fresnel Zone Plate, herein called a Tiered Fresnel Mirror TFM, with a focal length on the order of a meter is studied for use as the mirror(s) in a Fabry-Perot interferometer type of laser. The relative phase transition within the individual zones (ideally smooth from zero to pi ) is stair-stepped or tiered in the longitudinal direction of the mirror. Within an individual zone the step height is constrained to a constant whereas the width of the tiers are monotonically decreased when traversing radially outward so that the overall profile follows the ideal smooth curve. The effectiveness of the number of tiers per zone, measured by the loss per pass or round-trip, varies from a Plane Mirror (zero tiers per zone) to a Spherical Mirror (an infinite number of zones per tier). The Fox and Li iterative method of determining the E-Field as the beam propagates back and forth is applied to an empty cavity resonator to determine the diffraction loss. A computer program is written to investigate the diffraction loss of various mirror configurations. The performance of the TFM is found to be not as efficient as the Spherical Mirror (the number of tiers per zone is shown to be a major variable) but may be tolerable under applications of a moderately high gain laser medium. The Gaussian Fundamental mode is easier to maintain since the higher order modes have a higher loss per round trip. The manufacture of the TFM can be incorporated easily into an IC process thereby making the cost of the novel mirror relatively cheap when produced in quantities. A major cost variable is again the number of tiers per zone which is proportional to the number of processing steps. The TFM's performance with respect to the etch depth of the steps in the mirror's stair-stepped profile is simulated and found to be a very doable etch with the current plasma etch technology.

Orthokeratology (OK) is the reduction, modification or elimination of myopia through application of contact lenses. With the development of high Dk/t lens materials, overnight therapy has become the modality of choice for OK. Overnight OK lens wear has been previously investigated in terms of its efficacy to reduce myopia. However, the underlying effects of overnight OK lens wear on the human cornea have received less attention. As well as the clinical efficacy of overnight OK, this study investigated the effects of overnight OK on topographical corneal thickness and the overnight corneal edema response, and corneal tissue changes with overnight OK. Eighteen subjects participated as the OK lens-wearing group, wearing BE lenses (UltraVision, Brisbane, Queensland) in both eyes. A further ten subjects participated as control subjects, wearing conventional rigid lenses (J-Contour, UltraVision) in the right eye (RE) only. The left eye (LE) acted as a non-lens-wearing control. Both groups wore lenses overnight only, with no lens wear during the day. Measurements were conducted at baseline then on day 1, 4, 10, 30, 60, and 90 for the OK lens-wearing eyes; and up to day 30 for the control group, in the morning (after overnight lens wear) and in the evening (after 8-10 hours of lens removal). Variables measured included best vision sphere (BVS), unaided logMAR visual acuity (VA), refractive astigmatism, apical corneal power (ACP), simulated K readings (Medmont E300 corneal topographer), topographical corneal thickness (Holden-Payor optical pachometer), and keratocyte and endothelial cell densities (ConfoScan2 confocal microscope). Approximately 75% of myopia was corrected after the first night of OK lens wear and the changes in refractive error stabilised by day 10. By day 90, myopia reduction averaged 2.54 ?? 0.63 D. This was associated with significant improvement in unaided VA of about 82% after the first night of lens wear. There was no change in refractive astigmatism over the 3-month period. There was significant reduction in ACP in the OK lens-wearing eyes after the first night of lens wear, which accounted for more than 70% of the total ACP change over the 3-month period (RE: -2.16 ?? 0.53 D; LE: -2.11 ?? 0.86 D). There was significant central epithelial thinning (about 30%) and significant thickening (about 3%) in the mid-peripheral stroma in the OK lens-wearing eyes. Significant central epithelial thinning was found after the first night of lens wear while thickening in the mid-peripheral stroma reached statistical significance by day 4. Further analysis suggests that topographical corneal thickness changes account for the refractive error changes with overnight OK lens wear, rather than corneal bending. The central overnight stromal edema response was significantly reduced in the OK lens-wearing eyes (1.2 ?? 0.5%) to a level lower than in the conventional RGP (6.2 ?? 1.2%) and non-lens-wearing eyes (2.5 ?? 0.9%) in the control group. Mid-peripheral and peripheral stromal edema responses showed similar levels to those predicted based on lens Dk/t. A single overnight wear of BE and Paragon Corneal Refractive Therapy (CRT) lenses showed that the edema response to BE lens wear is significantly less than in the CRT lens-wearing eyes (BE: 2.5 ?? 0.7%; CRT 3.5 ?? 1.3%) immediately on eye opening. No significant changes were found in either central stromal keratocyte or endothelial cell densities in either OK or control groups over the study period. In conclusion, overnight OK lens wear induces significant reductions in myopia after the first night of lens wear associated with improvement in unaided VA. Overnight OK lens wear causes significant thinning in the central epithelium and significant mid-peripheral stromal thickening which results in flattening of the central cornea and steepening in the mid-periphery. Although there were no significant changes in central stromal keratocyte and endothelial cell densities, thinning of the central epithelial layer raises concerns regarding the safety of the procedure, especially with the alarming number of corneal infections reported recently in the literature.