Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 43 for “"Defocus"”.
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A low-cost defocus blur module for video rate quantified 3D imaging
Existing three-dimensional surface imaging systems are expensive, difficult to use, time consuming, and do not always provide the best accuracy or resolution. By using an offset aperture on a rotating disc, the 3D Monocular Imaging System provides a fast, portable, accurate, and cheap method of 3D …
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Estimation of Defocus Blur in Virtual Environments Comparing Graph Cuts and Convolutional Neural Network
… VR and AR, self-driving cars etc. Using the defocus blur of a camera lens is one of the methods of depth estimation. In this thesis, we have researched this technique in virtual environments. Virtual datasets have been created for this purpose. In this research, we have applied graph cuts and …
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Physiological responses of human retina and choroid to retinal image defocus: Implications for myopia
… and choroid have been implicated in detecting defocus and relaying information to the sclera to control eye size and thus maintain emmetropia. However, the mechanisms underlying retinal and choroidal responses to defocus remain unclear. Aims: To quantify and localise electrophysiological …
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A low complexity representation of the coherent point spread function in the presence of aberrations and arbitrarily large defocus
… number of aberrations and arbitrary large defocus simultaneously. We present an upper bound for the complexity and the convergence rate of this method. We also compare the cost and accuracy of this method to traditional ones and show the efficiency of our method through these comparisons. …
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Depth From Defocused Motion
Motion in depth and/or zooming causes defocus blur. This work presents a solution to the problem of using defocus blur and optical flow information to compute depth at points that defocus when they move. We first formulate a novel algorithm which recovers defocus blur and affine parameters …
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Analysis and transfer of photographic viewpoint and appearance
… and one contribution that magnifies existing defocus given a single photo. First, we address the challenge of viewpoint matching for rephotography. Our interactive, computer-vision-based technique helps users match the viewpoint of a reference photograph at capture time. Next, we focus on the …
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Software simulation of depth of field effects in video from small aperture cameras
… parameters of the effect (such as the amount of defocus, aperture shape, and defocus plane) and allows the effect to be used even on hardware which would not typically allow for depth of field. In addition, because it is a completely post processing technique and requires no change in capture …
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Peripheral Refractive Error and its Association with Myopia Development and Progression. An examination of the role that peripheral retinal defocus may play in the origin and progression of myopia
Purpose: Currently there are attempts to slow myopia progression by manipulating peripheral refractive error. This study proposed to establish the distribution of peripheral refractive errors in hyperopic, emmetropic and myopic children and to test the hypothesis that relative peripheral hyperopia …
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Point Spread Function Engineering for Scene Recovery
… due to a number of reasons, including defocus, lens aberration, diffraction, atmospheric turbulence, object motion, and etc. Image blur is often formulated as a convolution of the latent blur-free image and a PSF, and deconvolution (or deblurring) techniques have to be used to recover …
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Three dimensional moving pictures with a single imager and microfluidic lens
… is inferred using a new Extended Depth from Defocus (EDfD), and defocus is achieved at movie speeds with a microfluidic lens. Camera non-uniformities from both lens and sensor pipeline are analysed. The findings of some lens effects can be compensated for, but noise has the detrimental …
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Functional aspects of blur adaptation in human vision. A study of the mechanism of blur adaptation in human vision - its origin and scope evidenced using subjective and objective procedures.
… adaptation to blur improves visual acuity under defocused conditions. This phenomenon has been successfully demonstrated using subjective measures of acuity and is known as blur adaptation. This study investigates aspects of the mechanism of blur adaptation in human vision using subjective and …
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Interferometric Synthetic Aperture Microscopy
… that lie outside of the focus because the defocus and diffraction effects are not accounted for in the processing. These problems occur because of the lack of comprehensive models to include the scattering effects in the processing. In this dissertation, a new modality in three-dimensional …
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Quantification of the Depth-of-Field in a Self-Aligned Focusing Schlieren System
… of the SAFS system changes gradually with defocus, depends strongly on direction, and is influenced by diffraction from the Ronchi ruling in addition to defocus blur. Comparison with conventional depth-of-field definitions shows that no single geometric limit fully describes the measured …
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Smart photonics in imaging and sensing
… ECVFL based sensors. An active Depth from Defocus (DFD) system is proposed next, which uses coherent conditioned illumination to provide a sharpness retaining projection pattern over multiple target planes to aid the DFD computation procedure. Furthermore, the camera of the proposed DFD …
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Programmable Aperture Photography: An investigation into applications and methods
… years for use in various applications such as defocus deblurring, depth estimation and light field acquisition. Traditional coded aperture masks are constructed from static materials such as cardboard and cannot be altered once their shapes have been defined. These masks are then physically …
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Assessment of Ocular Accommodation in Humans
… further assessment of accommodative speeds. Defocus curves are used for assessing accommodation and depth-of-focus; the work presented explores the use of non-linear regression models to define the most appropriate method of assessing defocus curves in phakic subjects, and pseudophakic …
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First-Year Writing Ungraded Study At Eastern Kentucky University
Ungrading helps defocus the need for a grade within a classroom by helping students focus more on the feedback they receive within their First-Year Writing program. Ungrading uses self-assessments, grade rubrics, contracts, minimal grading, and portfolios to help give students feedback without the …
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The development of a predictive autofocus algorithm using a general image formation model
… in the presence of aberrations, in particular defocus. The extension of the model to include astigmatism is also included. The signals used are related to the ratios of the Fourier transforms of images captured under different operating conditions. Methods are developed for working with these …
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An algorithm for rapid measurement of aberrations in pairs of out-of-focus images
… by simultaneously fitting a pair of oppositely defocused images to a mostly analytic model. I develop the model and describe its software implementation in detail, and then report on the results of tests with simulated and real data. This technique is able to extract the aberrations from …
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Estimation de l'échelle absolue par vision passive monofocale et application à la mesure 3D de néoplasies en imagerie coloscopique
… in detail state of the art DfD (Depth-from-Defocus) and DfF (Depth-from-Defocus) approaches. They are passive computer vision techniques that enable us to resolve scale ambiguity. Our core contribution is introduced in the following chapter. We define the Infocus-Breakpoint (IB) that allows …
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