This thesis consists of two parts: a report on the use of a binocular Shack-Hartmann (SH) sensor to study the dynamic correlation of ocular aberrations; and the application of an adaptive optics (AO) system to investigate the effect of the manipulation of aberrations on the accommodation control. The binocular SH sensor consists of one laser source and one camera to reduce system cost and complexity. Six participants took part in this study. Coherence function analysis showed that coherence values were dependent on the subject, aberration and frequency component. Inter-ocular correlations of the aberration dynamics were fairly weak for all participants. Binocular and monocular viewing conditions produced similar wavefront error dynamics. The AO system has a dual wavefront sensing channel. The extra sensing channel permits direct measurement of the eye's aberrations independent of the deformable mirror. Dynamic correction of aberrations during steady-state fixation did not affect the accommodation microfluctuations, possibly due to the prior correction of the static aberration level and/or the limited correction bandwidth. The inversion of certain aberrations during dynamic accommodation affected the gain and latency of accommodation response (AR), suggesting that the eye used the aberrations to guide its initial path of accommodative step response. Corrections of aberrations at various temporal locations of AR cycle produced subject- and aberration-dependent results. The gain and phase lag of the AR to a sinusoidally moving target were unaffected by aberration correction. The predictable nature of the target had been suggested as the reason for its failure to produce any significant effect on the AR gain and phase lag.

Reconstruction of continuous signals from a number of their discrete samples is central to digital signal processing. Digital devices can only process discrete data and thus processing the continuous signals requires discretization. After discretization, possibility of unique reconstruction of the source signals from their samples is crucial. The classical sampling theory provides bounds on the sampling rate for unique source reconstruction, known as the Nyquist sampling rate. Recently a new sampling scheme, Compressive Sensing (CS), has been formulated for sparse signals. CS is an active area of research in signal processing. It has revolutionized the classical sampling theorems and has provided a new scheme to sample and reconstruct sparse signals uniquely, below Nyquist sampling rates. A signal is called (approximately) sparse when a relatively large number of its elements are (approximately) equal to zero. For the class of sparse signals, sparsity can be viewed as prior information about the source signal. CS has found numerous applications and has improved some image acquisition devices. Interesting instances of CS can happen, when apart from sparsity, side information is available about the source signals. The side information can be about the source structure, distribution, etc. Such cases can be viewed as extensions of the classical CS. In such cases we are interested in incorporating the side information to either improve the quality of the source reconstruction or decrease the number of the required samples for accurate reconstruction. A general CS problem can be transformed to an equivalent optimization problem. In this thesis, a special case of CS with side information about the feasible region of the equivalent optimization problem is studied. It is shown that in such cases uniqueness and stability of the equivalent optimization problem still holds. Then, an efficient reconstruction method is proposed. To demonstrate the practical value of the proposed scheme, the algorithm is applied on two real world applications: image deblurring in optical imaging and surface reconstruction in the gradient field. Experimental results are provided to further investigate and confirm the effectiveness and usefulness of the proposed scheme.

This thesis consists of two parts: a report on the use of a binocular Shack-Hartmann (SH) sensor to study the dynamic correlation of ocular aberrations; and the application of an adaptive optics (AO) system to investigate the effect of the manipulation of aberrations on the accommodation control. The binocular SH sensor consists of one laser source and one camera to reduce system cost and complexity. Six participants took part in this study. Coherence function analysis showed that coherence values were dependent on the subject, aberration and frequency component. Inter-ocular correlations of the aberration dynamics were fairly weak for all participants. Binocular and monocular viewing conditions produced similar wavefront error dynamics. The AO system has a dual wavefront sensing channel. The extra sensing channel permits direct measurement of the eye¿s aberrations independent of the deformable mirror. Dynamic correction of aberrations during steady-state fixation did not affect the accommodation microfluctuations, possibly due to the prior correction of the static aberration level and/or the limited correction bandwidth. The inversion of certain aberrations during dynamic accommodation affected the gain and latency of accommodation response (AR), suggesting that the eye used the aberrations to guide its initial path of accommodative step response. Corrections of aberrations at various temporal locations of AR cycle produced subject- and aberration-dependent results. The gain and phase lag of the AR to a sinusoidally moving target were unaffected by aberration correction. The predictable nature of the target had been suggested as the reason for its failure to produce any significant effect on the AR gain and phase lag.

No description available.

Adaptive optic technology has revolutionized real time correction of wavefront aberrations. Optofluidic based applied optic devices have offered an opportunity to produce flexible refractive lenses in the correction of wavefronts. Fluidic lenses have superiority relative to their solid lens counterparts in their capabilities of producing tunable optical systems, that when synchronized, can produce real time variable systems with no moving parts. We have developed optofluidic fluidic lenses for applications of applied optical devices, as well as ophthalmic optic devices. The first half of this dissertation discusses the production of fluidic lenses as optical devices. In addition, the design and testing of various fluidic systems made with these components are evaluated. We begin with the creation of spherical or defocus singlet fluidic lenses. We then produced zoom optical systems with no moving parts by synchronizing combinations of these fluidic spherical lenses. The variable power zoom system incorporates two singlet fluidic lenses that are synchronized. The coupled device has no moving parts and has produced a magnification range of 0.1 x to 10 x or a 20 x magnification range. The chapter after fluidic zoom technology focuses on producing achromatic lens designs. We offer an analysis of a hybrid diffractive and refractive achromat that offers discrete achromatized variable focal lengths. In addition, we offer a design of a fully optofluidic based achromatic lens. By synchronizing the two membrane surfaces of the fluidic achromat we develop a design for a fluidic achromatic lens.The second half of this dissertation discusses the production of optofluidic technology in ophthalmic applications. We begin with an introduction to an optofluidic phoropter system. A fluidic phoropter is designed through the combination of a defocus lens with two cylindrical fluidic lenses that are orientated 45° relative to each other. Here we discuss the designs of the fluidic cylindrical lens coupled with a previously discussed defocus singlet lens. We then couple this optofluidic phoropter with relay optics and Shack-Hartmann wavefront sensing technology to produce an auto-phoropter device. The auto-phoropter system combines a refractometer designed Shack-Hartmann wavefront sensor with the compact refractive fluidic lens phoropter. This combination allows for the identification and control of ophthalmic cylinder, cylinder axis, as well as refractive error. The closed loop system of the fluidic phoropter with refractometer enables for the creation of our see-through auto-phoropter system. The design and testing of several generations of transmissive see-through auto-phoropter devices are presented in this section.

La performance d'un système d'optique adaptative (AO) est intrinsèquement liée à sa capacité à mesurer les déformations subies par le front d'onde incident lors de sa traversée de l'atmosphère. Or un certain nombre de limitations restreignent l'efficacité de cette analyse de front d'onde. Les plus importantes sont le bruit de mesure et l'anisoplanétisme. Le premier limite la magnitude des objets astronomiques pouvant servir de guides aux systèmes d'AO, tandis que le second restreint leur champ corrigé à quelques dizaines de secondes d'arc, du fait de la distribution volumique de la turbulence atmosphérique. A elles deux, ces limitations réduisent à quelques pourcents la couverture de ciel des instruments assistés par AO. Pour cette raison, les nouvelles générations d'optiques adaptatives ont pour objectif soit la très haute performance, impliquant entre autres une bonne robustesse au bruit de mesure, soit l'élargissement du champ corrigé, impliquant la connaissance de la répartition 3D de la turbulence atmosphérique. Pour ces systèmes d'AO à large champ, il est indispensable d'utiliser plusieurs directions d'analyse. La problématique de l'analyse de front d'onde s'articule alors autour de trois pôles : les étoiles guides dont on dispose pour effectuer la multi-analyse, le concept d'analyse de front d'onde considéré pour mesurer le volume de turbulence et la capacité des senseurs de front d'onde à fournir des mesures de qualité. L'objectif de cette thèse est d'étudier chacun de ces trois aspects. Ainsi, une redéfinition de la notion de couverture de ciel est proposée pour les AO à large champ, permettant de prendre en compte le nombre d'étoiles guides et leur magnitude, mais également la fraction du champ scientifique qu'elles permettent de couvrir, le concept d'analyse de front d'onde considéré et l'objectif de performance de l'instrument. Par ailleurs une étude comparative des concepts d'analyse de front d'onde Star Oriented et Layer Oriented est présentée, sur laquelle on s'appuie pour proposer une optimisation de chaque concept. On montre ainsi qu'une fois optimisés ils présentent tous deux des performances très proches. Enfin, on propose dans un troisième temps une étude comparative de plusieurs estimateurs de pente pour l'analyseur Shack-Hartmann. On étudie en particulier l'estimateur centre de gravité pondéré, qui offre à la fois une bonne robustesse au bruit et de bonnes propriétés de linéarité. Cette dernière étude est utile aussi bien pour l'AO à large champ que pour l'AO à très haute performance.

No description available.

Lasers which operate at both high average power and energy are in demand for a wide range of applications such as materials processing, directed energy and EUV generation. Presented in this dissertation is a high-power 1 μm ytterbium-based hybrid laser system with temporally tailored pulse shaping capability and up to 62 mJ pulses, with the expectation the system can scale to higher pulse energies. This hybrid system consists of a low power fiber seed and pre-amplifier, and a solid state thin-disk regenerative amplifier. This system has been designed to generate high power temporally tailored pulses on the nanosecond time scale. Temporal tailoring and spectral control are performed in the low power fiber portion of the system with the high pulse energy being generated in the regenerative amplifier. The seed system consists of a 1030 nm fiber-coupled diode, which is transmitted through a Mach-Zehnder-type modulator in order to temporally vary the pulse shape. Typical pulses are 20-30 ns in duration and have energies of ~0.2 nJ from the modulator. These are amplified in a fiber pre-amplifier stage to ~100 nJ before being used to seed the free-space Yb:YAG thin-disk regenerative amplifier. Output pulses have maximum demonstrated pulse energies of 62 mJ with 20 ns pulse after ~250 passes in the cavity. The effects of thermal distortion in laser and passive optical materials are also. Generally the development of high power and high energy lasers is limited by thermal management strategies, as thermally-induced distortions can degrade laser performance and potentially cause catastrophic damage. Novel materials, such as optical ceramics, can be used to mitigate thermal distortions; however, thorough analysis is required to optimize their fabrication and minimize thermal distortions. iv Using a Shack-Hartmann wavefront sensor (SHWFS), it is possible to analyze the distortion induced in passive and doped optical elements by high power lasers. For example, the thin-disk used in the regenerative amplifier is examined in-situ during CW operation (up to 2 kW CW pump power). Additionally, passive oxide-based optical materials and Yb:YAG optical ceramics are also examined by pumping at 2 and 1 μm respectively to induce thermal distortions which are analyzed with the SHWFS. This method has been developed as a diagnostic for the relative assessment of material quality, and to grade differences in ceramic laser materials associated with differences in manufacturing processes and/or the presence of impurities. In summation, this dissertation presents a high energy 1 μm laser system which is novel in its combination of energy level and temporal tailoring, and an analysis of thermal distortions relevant to the development of high power laser systems.

Optical testing in adverse environments, ophthalmology and applications where characterization by curvature is leveraged all have a common goal: accurately estimate wavefront shape. This dissertation investigates wavefront sensing techniques as applied to optical testing based on gradient and curvature measurements. Wavefront sensing involves the ability to accurately estimate shape over any aperture geometry, which requires establishing a sampling grid and estimation scheme, quantifying estimation errors caused by measurement noise propagation, and designing an instrument with sufficient accuracy and sensitivity for the application. Starting with gradient-based wavefront sensing, a zonal least-squares wavefront estimation algorithm for any irregular pupil shape and size is presented, for which the normal matrix equation sets share a pre-defined matrix. A Gerchberg–Saxton iterative method is employed to reduce the deviation errors in the estimated wavefront caused by the pre-defined matrix across discontinuous boundary. The results show that the RMS deviation error of the estimated wavefront from the original wavefront can be less than λ/130~ λ/150 (for λ equals 632.8nm) after about twelve iterations and less than λ/100 after as few as four iterations. The presented approach to handling irregular pupil shapes applies equally well to wavefront estimation from curvature data. A defining characteristic for a wavefront estimation algorithm is its error propagation behavior. The error propagation coefficient can be formulated as a function of the eigenvalues of the wavefront estimation-related matrices, and such functions are established for each of the basic estimation geometries (i.e. Fried, Hudgin and Southwell) with a serial numbering scheme, where a square sampling grid array is sequentially indexed row by row. The results show that with the wavefront piston-value fixed, the odd-number grid sizes yield lower error propagation than the even-number grid sizes for all geometries. The Fried geometry either allows sub-sized wavefront estimations within the testing domain or yields a two-rank deficient estimation matrix over the full aperture; but the latter usually suffers from high error propagation and the waffle mode problem. Hudgin geometry offers an error propagator between those of the Southwell and the Fried geometries. For both wavefront gradient-based and wavefront difference-based estimations, the Southwell geometry is shown to offer the lowest error propagation with the minimum-norm least-squares solution. Noll’s theoretical result, which was extensively used as a reference in the previous literature for error propagation estimate, corresponds to the Southwell geometry with an odd-number grid size. For curvature-based wavefront sensing, a concept for a differential Shack-Hartmann (DSH) curvature sensor is proposed. This curvature sensor is derived from the basic Shack-Hartmann sensor with the collimated beam split into three output channels, along each of which a lenslet array is located. Three Hartmann grid arrays are generated by three lenslet arrays. Two of the lenslets shear in two perpendicular directions relative to the third one. By quantitatively comparing the Shack-Hartmann grid coordinates of the three channels, the differentials of the wavefront slope at each Shack-Hartmann grid point can be obtained, so the Laplacian curvatures and twist terms will be available. The acquisition of the twist terms using a Hartmann-based sensor allows us to uniquely determine the principal curvatures and directions more accurately than prior methods. Measurement of local curvatures as opposed to slopes is unique because curvature is intrinsic to the wavefront under test, and it is an absolute as opposed to a relative measurement. A zonal least-squares-based wavefront estimation algorithm was developed to estimate the wavefront shape from the Laplacian curvature data, and validated. An implementation of the DSH curvature sensor is proposed and an experimental system for this implementation was initiated. The DSH curvature sensor shares the important features of both the Shack-Hartmann slope sensor and Roddier’s curvature sensor. It is a two-dimensional parallel curvature sensor. Because it is a curvature sensor, it provides absolute measurements which are thus insensitive to vibrations, tip/tilts, and whole body movements. Because it is a two-dimensional sensor, it does not suffer from other sources of errors, such as scanning noise. Combined with sufficient sampling and a zonal wavefront estimation algorithm, both low and mid frequencies of the wavefront may be recovered. Notice that the DSH curvature sensor operates at the pupil of the system under test, therefore the difficulty associated with operation close to the caustic zone is avoided. Finally, the DSH-curvature-sensor-based wavefront estimation does not suffer from the 2π-ambiguity problem, so potentially both small and large aberrations may be measured.

Ce travail a comme but l'étude de nouveaux cristaux dopés à l'ion ytterbium, pour le développement de lasers efficaces (et éventuellement accordables) émettant vers 1 µm. La première partie traite des performances laser en pompage par diode de forte puissance (10-15 W) de nouveaux cristaux : l'Yb:GGG, l'Yb:GdCOB, l'Yb:BOYS (et l'Yb:CaBOYS), l'Yb:SYS et l'Yb:YSO. L'efficacité, l'accordabilité, et le comportement thermique de ces matériaux est discutée, et illustrée, lorsque cela est pertinent, par une comparaison entre matériaux voisins. Les effets thermiques limitent la montée en puissance dans la plupart de ces nouveaux matériaux : leur étude détaillée fait l'objet de la seconde partie. Nous commençons par une synthèse théorique sur les effets thermiques et thermomécaniques dans les lasers solides. Après une description des différentes méthodes expérimentales d'investigation des effets thermiques, nous décrivons le banc de mesure que nous avons mis en place. Il est basé sur un analyseur de front d'onde de Shack-Hartmann, et il permet la mesure des lentilles thermiques (et de leurs aberrations) dans des configurations de pompage longitudinal, en présence (ou non) d'effet laser. Nous décrivons les caractéristiques et les limitations de cet outil en détail. Des mesures de lentilles thermiques sont ensuite rapportées, pour la première fois, dans des matériaux dopés à l'ytterbium. Nous avons mis en évidence d'importants effets non radiatifs qui contribuent à la charge thermique, contrairement à ce qui est généralement admis. Nous détaillons alors comment, avec un modèle analytique simple, on peut déduire de ces mesures le rendement quantique et le coefficient thermo-optique des matériaux considérés. Nous avons également mis en évidence expérimentalement l'influence de la longueur d'onde laser sur la charge thermique, la réduction des effets thermiques dans des cristaux composites, ou encore la contribution significative de l'effet photoélastique à la lentille thermique dans l'Yb:GdCOB.