| 1. |
- Abramson, Nils H.
(författare)
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Holodiagram : elliptic visualizing interferometry, relativity, and light-in-flight
- 2014
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 53:11, s. 2398-2404
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Tidskriftsartikel (refereegranskat)abstract
- In holographic interferometry, there is usually a static distance separating the point of illumination and the point of observation. In Special Relativity, this separation is dynamic and is caused by the velocity of the observer. The corrections needed to compensate for these separations are similar in the two fields. We use the ellipsoids of the holodiagram for measurement and in a graphic way to explain and evaluate optical resolution, gated viewing, radar, holography, three-dimensional interferometry, Special Relativity, and light-in-flight recordings. Lorentz contraction together with time dilation is explained as the result of the eccentricity of the measuring ellipsoid, caused by its velocity. The extremely thin ellipsoid of the very first light appears as a beam aimed directly at the observer, which might explain the wave or ray duality of light and entanglement. Finally, we introduce the concept of ellipsoids of observation.
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| 2. |
- Bergström, Per, et al.
(författare)
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Dual-wavelength digital holography : single-shot shape evaluation using speckle displacements and regularization
- 2014
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Ingår i: Applied Optics. - : Optical Society of America. - 1559-128X .- 2155-3165 .- 0003-6935 .- 1539-4522. ; 53:1, s. 123-131
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Tidskriftsartikel (refereegranskat)abstract
- This paper discusses the possibility of evaluating the shape of a free-form object in comparison with its shape prescribed by a CAD model. Measurements are made based on a single-shot recording using dual-wavelength holography with a synthetic wavelength of 1.4 mm. Each hologram is numerically propagated to different focus planes and correlated. The result is a vector field of speckle displacements that is linearly dependent on the local distance between the measured surface and the focus plane. From these speckle displacements, a gradient field of the measured surface is extracted through a proportional relationship. The gradient field obtained from the measurement is then aligned to the shape of the CAD model using the iterative closest point (ICP) algorithm and regularization. Deviations between the measured shape and the CAD model are found from the phase difference field, giving a high precision shape evaluation. The phase differences and the CAD model are also used to find a representation of the measured shape. The standard deviation of the measured shape relative the CAD model varies between 7 and 19 μm, depending on the slope.
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| 3. |
- Bhaduri, Basanta, et al.
(författare)
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Simultaneous measurement of translation and tilt using digital speckle photography
- 2010
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 49:18, s. 3573-3579
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Tidskriftsartikel (refereegranskat)abstract
- A Michelson-type digital speckle photographic system has been proposed in which one light beam produces a Fourier transform and another beam produces an image at a recording plane, without interfering between themselves. Because the optical Fourier transform is insensitive to translation and the imaging technique is insensitive to tilt, the proposed system is able to simultaneously and independently determine both surface tilt and translation by two separate recordings, one before and another after the surface motion, without the need to obtain solutions for simultaneous equations. Experimental results are presented to verify the theoretical analysis.
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| 4. |
- Borgentun, Carl, 1979, et al.
(författare)
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Full characterization of a high-power semiconductor disk laser beam with simultaneous capture of optimally sized focus and farfield
- 2011
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 50:12, s. 1640-1649
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Tidskriftsartikel (refereegranskat)abstract
- We report on a beam characterization method that is based on the simultaneous measurement of the focus field and the farfield, thus avoiding problems with beam fluctuations during the measurement. By using reflections from both sides of a planoconvex lens, the method implements two branches of an optical system working simultaneously. Also, by letting the planoconvex lens be antireflection treated, and by allowing for both of the reflected fields to fill large and approximately equal areas on a camera detector array, the method significantly lowers the intensity onto the detector array, thus minimizing the need for additional disturbing attenuation filters to avoid camera saturation. In the numerical retrieval of the phase distribution, based on the measured intensity distributions of the focus and farfield, iterative propagation between the two branches is performed. The phase retrieval uses the two-step algorithm for the numerical field propagation conveniently providing an arbitrary choice of sampling distance in each plane.
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| 5. |
- Casselgren, Johan, et al.
(författare)
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Polarization resolved classification of winter road condition in the near-infrared region
- 2012
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 51:15, s. 3036-3045
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Tidskriftsartikel (refereegranskat)abstract
- Three different configurations utilizing polarized short-wave infrared light to classify winter road conditions have been investigated. In the first configuration, polarized broadband light was detected in the specular and backward directions, and the quotient between the detected intensities was used as the classification parameter. Best results were obtained for the SS-configuration. This sensor was shown to be able to distinguish between the smooth road conditions of water and ice from the diffuse road conditions of snow and dry asphalt with a probability of wrong classification as low as 7%. The second sensor configuration was a pure backward architecture utilizing polarized light with two distinct wavelengths. This configuration was shown to be effective for the important problem of distinguishing water from ice with a probability of wrong classification of only 1.5%. The third configuration was a combination of the two previous ones. This combined sensor utilizing bispectral illumination and bidirectional detection resulted in a probability of wrong classification as low as 2% among all four surfaces.
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| 6. |
- Degerman Engfeldt, Johnny, et al.
(författare)
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Methodology for measuring current distribution effects in electrochromic smart windows
- 2011
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 50:29, s. 5639-5646
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Tidskriftsartikel (refereegranskat)abstract
- Electrochromic (EC) devices for use as smart windows have a large energy-saving potential when used in the construction and transport industries. When upscaling EC devices to window size, a well-known challenge is to design the EC device with a rapid and uniform switching between colored (charged) and bleached (discharged) states. A well-defined current distribution model, validated with experimental data, is a suitable tool for optimizing the electrical system design for rapid and uniform switching. This paper introduces a methodology, based on camera vision, for experimentally validating EC current distribution models. The key is the methodology's capability to both measure and simulate current distribution effects as transmittance distribution. This paper also includes simple models for coloring (charging) and bleaching (discharging), taking into account secondary current distribution with charge transfer resistance and ohmic effects. Some window-size model predictions are included to show the potential for using a validated EC current distribution model as a design tool.
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| 7. |
- Delacroix, Christian, et al.
(författare)
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Design, manufacturing, and performance analysis of mid-infrared achromatic half-wave plates with diamond subwavelength gratings
- 2012
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 51:24, s. 5897-5902
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present a solution for creating robust monolithic achromatic half-wave plates (HWPs) for the infrared, based on the form birefringence of subwavelength gratings (SWGs) made out of diamond. We use the rigorous coupled wave analysis to design the gratings. Our analysis shows that diamond, besides its outstanding physical and mechanical properties, is a suitable substrate to manufacture mid-infrared HWPs, thanks to its high refractive index, which allows etching SWGs with lower aspect ratio. Based on our optimized design, we manufactured a diamond HWP for the 11-13.2 mu m region, with an estimated mean retardance similar to 3.143 +/- 0.061 rad ( 180.08 +/- 3.51 degrees). In addition, an antireflective grating was etched on the backside of the wave plate, allowing a total transmittance between 89% and 95% over the band.
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| 8. |
- Dong, Lin, et al.
(författare)
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Photoluminescence from quasi-type-II spherical CdSe-CdS core-shell quantum dots
- 2013
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 52:1, s. 105-109
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Tidskriftsartikel (refereegranskat)abstract
- Spherical CdSe-CdS core-shell quantum dots (QDs) are found to be flexible in the transition between the type-I regime and the type-II regime with different core/shell dimensions. The quasi-type-II feature of the colloidal dots is confirmed with time-resolved photoluminescence (PL) measurements. Two recombination paths of the excitons with significantly different decay rates are observed and analyzed. The spherical CdSe-CdS core-shell QDs are numerically simulated to investigate the carrier separation. A relatively long radiative lifetime and high degree of spatial carrier separation provide good potential to achieve lasing under continuous-wave excitation. Amplified spontaneous emission at room temperature is detected from the QDs embedded in the polymer matrix. It is shown that a larger shell thickness results in a lower pumping threshold, while a smaller shell thickness leads to higher PL efficiency.
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| 9. |
- Emadi, A., et al.
(författare)
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Linear variable optical filter-based ultraviolet microspectrometer
- 2012
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 51:19, s. 4308-4315
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Tidskriftsartikel (refereegranskat)abstract
- An IC-compatible linear variable optical filter (LVOF) for application in the UV spectral range between 310 and 400 nm has been fabricated using resist reflow and an optimized dry-etching. The LVOF is mounted on the top of a commercially available CMOS camera to result in a UV microspectrometer. A special calibration technique has been employed that is based on an initial spectral measurement on a xenon lamp. The image recorded on the camera during calibration is used in a signal processing algorithm to reconstruct the spectrum of the mercury lamp and the calibration data is subsequently used in UV spectral measurements. Experiments on a fabricated LVOF-based microspectrometer with this calibration approach implemented reveal a spectral resolution of 0.5 nm.
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| 10. |
- Gustafsson Coppel, Ludovic, et al.
(författare)
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Determination of quantum efficiency in fluorescing turbid media
- 2011
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 50:17, s. 2784-2792
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Tidskriftsartikel (refereegranskat)abstract
- A method is proposed to estimate the optical parameters in a fluorescing turbid medium with strong absorption for which traditional Kubelka–Munk theory is not applicable, using a model for the radiative properties of optically thick fluorescent turbid media of finite thickness proposed in 2009[J. Opt. Soc. Am. A26, 1896 (2009)JOAOD60740-323210.1364/JOSAA.26.001896]. The method is successfully applied to uncoated papers with different thicknesses. It is found that the quantum efficiency of fluorescent whitening agents (FWAs) is nearly independent of the fiber type, FWA type, FWA concentration, and filler additive concentration used in this study. The results enable an estimation of the model parameters as function of the FWA concentration and substrate composition. This is necessary in order to use the model for optimizing fluorescence in the paper and textile industries.
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