| 1. |
- Akram, Muhammad Nadeem, et al.
(author)
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Improved wide-field emmetropic human eye model based on ocular wavefront measurements and geometry-independent gradient index lens
- 2018
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In: Optical Society of America. Journal A. - : Optical Society of America. - 1084-7529 .- 1520-8532. ; 35:11, s. 1954-1967
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Journal article (peer-reviewed)abstract
- There is a need to better understand the peripheral optics of the human eye and their correction. Current eye models have some limitations to accurately predict the wavefront errors for the emmetropic eye over a wide field. The aim here was to develop an anatomically correct optical model of the human eye that closely reproduces the wavefront of an average Caucasian-only emmetropic eye across a wide visual field. Using an optical design program, a schematic eye was constructed based on ocular wavefront measurements of the right eyes of thirty healthy young emmetropic individuals over a wide visual field (from 40° nasal to 40° temporal and up to 20° inferior field). Anatomical parameters, asymmetries, and dispersion properties of the eye’s different optical components were taken into account. A geometry-independent gradient index model was employed to better represent the crystalline lens. The RMS wavefront error, wavefront shapes, dominant Zernike coefficients, nasal-temporal asymmetries, and dispersion properties of the developed schematic eye closely matched the corresponding measured values across the visual field. The developed model can help in the design of wide-field ophthalmic instruments and is useful in the study and simulations of the peripheral optics of the human eye.
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| 2. |
- Börjeson, Charlie, et al.
(author)
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Implementing a non-4f relay system for Hartmann–Shack wavefront sensing
- 2022
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In: Journal of the Optical Society of America A. - : Optica Publishing Group. - 0740-3232 .- 1084-7529 .- 1520-8532. ; 40:6
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Journal article (peer-reviewed)abstract
- Hartmann–Shack wavefront sensors (HSWSs) are used in many disciplines to measure optical aberrations. Conventionally, the wavefront of interest is transferred onto the lenslet array of the HSWS with a telescopic 4f relay system. However, the 4f relay design restricts the choice of focal lengths and distances used for the relay system. In this paper, we describe a non-4f variant and demonstrate both theoretically and experimentally that its wavefront relaying properties equal that of a 4f system. We also present an alignment method for conjugating the wavefront with the lenslet array of the HSWS for both 4f and non-4f systems.
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| 3. |
- Cai, Yangjian, et al.
(author)
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Coincidence subwavelength fractional Fourier transform
- 2006
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In: Optical Society of America. Journal A. - 1084-7529 .- 1520-8532. ; 23:4, s. 835-841
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Journal article (peer-reviewed)abstract
- The coincidence subwavelength fractional Fourier transforms (FRTs) with entangled photon pairs and incoherent light radiation are introduced as an extension of the recently introduced coincidence FRT. Optical systems for implementing the coincidence subwavelength FRTs are designed. The width of the coincidence subwavelength FRT pattern is two times narrower than the width of the coincidence FRT. The coincidence subwavelength FRT with partially coherent light radiation is also studied numerically. Differences between the coincidence subwavelength FRT with entangled photon pairs and that with incoherent light radiation are discussed.
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| 4. |
- Calander, Nils, 1953
(author)
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Focused optical beams obtained at planar structures by an imaginary shift in position
- 2007
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In: Journal of the Optical Society of America A: Optics and Image Science, and Vision. - 1084-7529 .- 1520-8532. ; 24:9, s. 2513-2515
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Journal article (peer-reviewed)abstract
- A theory for focused optical beams at planar structures is described. It is an extension of a previous theory based on summation of plane waves. The focused beam is obtained by an imaginary shift in the position vector of the plane waves. It is well suited for calculations of electromagnetic fields at planar surface plasmon resonance structures excited by a focused optical beam.
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| 5. |
- Doelman, Reinier, et al.
(author)
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Identification of the dynamics of time-varying phase aberrations from time histories of the point-spread function
- 2019
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In: Optical Society of America. Journal A. - : OPTICAL SOC AMER. - 1084-7529 .- 1520-8532. ; 36:5, s. 809-817
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Journal article (peer-reviewed)abstract
- To optimally compensate for time-varying phase aberrations with adaptive optics, a model of the dynamics of the aberrations is required to predict the phase aberration at the next time step. We model the time-varying behavior of a phase aberration, expressed in Zernike modes, by assuming that the temporal dynamics of the Zernike coefficients can be described by a vector-valued autoregressive (VAR) model. We propose an iterative method based on a convex heuristic for a rank-constrained optimization problem, to jointly estimate the parameters of the VAR model and the Zernike coefficients from a time series of measurements of the point-spread function (PSF) of the optical system. By assuming the phase aberration is small, the relation between aberration and PSF measurements can be approximated by a quadratic function. As such, our method is a blind identification method for linear dynamics in a stochastic Wiener system with a quadratic nonlinearity at the output and a phase retrieval method that uses a time-evolution-model constraint and a single image at every time step. (c) 2019 Optical Society of America.
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| 6. |
- Ekberg, Peter, et al.
(author)
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Fast and accurate metrology of multi-layered ceramic materials by an automated boundary detection algorithm developed for optical coherence tomography data
- 2014
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In: Optical Society of America. Journal A. - 1084-7529 .- 1520-8532. ; 31:2, s. 217-226
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Journal article (peer-reviewed)abstract
- Optical coherence tomography (OCT) is useful for materials defect analysis and inspection with the additional possibility of quantitative dimensional metrology. Here, we present an automated image-processing algorithm for OCT analysis of roll-to-roll multilayers in 3D manufacturing of advanced ceramics. It has the advantage of avoiding filtering and preset modeling, and will, thus, introduce a simplification. The algorithm is validated for its capability of measuring the thickness of ceramic layers, extracting the boundaries of embedded features with irregular shapes, and detecting the geometric deformations. The accuracy of the algorithm is very high, and the reliability is better than 1 mu m when evaluating with the OCT images using the same gauge block step height reference. The method may be suitable for industrial applications to the rapid inspection of manufactured samples with high accuracy and robustness.
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| 7. |
- Freitag, Fabio Batista, et al.
(author)
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Effect of luminosity on color discrimination of dichromatic marmosets (Callithrix jacchus)
- 2012
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In: Optical Society of America. Journal A. - 1084-7529 .- 1520-8532. ; 29:2, s. A216-22
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Journal article (peer-reviewed)abstract
- Psychophysical data have shown that under mesopic conditions cones and rods can interact, improving color vision. Since electrophysiological data have suggested that rods of dichromatic marmosets appear to be active at higher luminance, we aimed to investigate the effect of different levels of sunlight on the foraging abilities of male dichromatic marmosets. Captive marmosets were observed under three different conditions, with respect to their performance in detecting colored food items against a green background. Compared to high and low light intensities, intermediate luminosities significantly increased detection of orange targets by male dichromats, an indication of rod intrusion.
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| 8. |
- Gerosa, Rodrigo M., et al.
(author)
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All-fiber high repetition rate microfluidic dye laser
- 2015
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In: Optica. - 2334-2536. ; 2:2, s. 186-193
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Journal article (peer-reviewed)abstract
- Optofluidic dye lasers may play a significant role in future laser applications in numerous areas, combining wavelength flexibility with integration and ease of operation. Nevertheless, no all-fiber integrated dye lasers have been demonstrated so far. In this paper, we report on a series of optofluidic all-fiber Rhodamine optical sources operating at a repetition rate as high as 1 kHz. Dye bleaching is avoided by circulating the Rhodamine dye during optical excitation. The laser radiation is extracted via conventional fibers that are spliced to the dye-filled capillary active medium. A tuneable amplified spontaneous emission source, a multimode laser, and a few transverse-mode laser are demonstrated by adjusting the setup. Threshold pump energies as low as similar to 1 mu J and slope efficiencies of up to mu 9% were obtained, indicating the potential for realworld applications in areas such as spectroscopy and biomedicine.
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| 9. |
- Gustafsson Coppel, Ludovic, 1975-, et al.
(author)
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Extension of the Stokes equation for layered constructions to fluorescent turbid media
- 2012
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In: Journal of the Optical Society of America A. - : Optical Society of America. - 1084-7529 .- 1520-8532. ; 29:4, s. 574-578
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Journal article (peer-reviewed)abstract
- Expressions relating the bispectral reflectance of a stack of n fluorescinglayers to each individual layer's reflectance and transmittance arederived. This theoretical framework is used together with recentlyproposed extensions of the Kubelka--Munk model to study the fluorescencefrom layered turbid media. For one layer over a reflecting background,the model is shown to give the same results as a previous model.The extension to n layers with different optical properties allowssimulating the bispectral reflectance from a pad of layered turbidmedia. The applicability of the model is exemplified with an optimizationof fluorophore distribution in layered turbid media.
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| 10. |
- Huntley, J.M., et al.
(author)
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Error-reduction methods for shape measurement by temporal phase unwrapping
- 1997
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In: Optical Society of America. Journal A. - 1084-7529 .- 1520-8532. ; 14:12, s. 3188-3196
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Journal article (peer-reviewed)abstract
- Temporal phase unwrapping is a method of analyzing fringe patterns in which the fringe phase at each pixel is measured and unwrapped as a function of time t. We propose two methods for improving the signal-to-noise ratio of the total phase change by incorporating data from the intermediate phase values. The first involves fitting the expected curve to the measured phase history; the second involves Fourier transformation of the corresponding phasors. The performance of these methods is compared both experimentally, with data from a fringe projector based on a spatial-light modulator, and numerically. It is shown that the optimum performance is given by the Fourier transform method. The best way to use the first method is with decreasing exponentially with time from its maximum value to zero; this provides significant improvements in reliability, accuracy, and computation time compared with the original temporal unwrapping algorithm
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