| 1. |
- Arwin, Hans, et al.
(författare)
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On the polarization of light reflected from beetle cuticle
- 2017
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Ingår i: MATERIALS TODAY-PROCEEDINGS. - : ELSEVIER SCIENCE BV. ; , s. 4933-4941
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Konferensbidrag (refereegranskat)abstract
- The use of Mueller matrices for studies of polarizing properties and cuticle structure of scarab beetles are partly reviewed. Specifically we show how the polarization of the reflected light can be quantified in terms of degree of polarization and ellipticity. It is also shown that sum decomposition of Mueller matrices reveals cuticle reflection characteristics in different spectral regions, e.g. in terms of mirrors and circular polarizers. With a differential decomposition of cuticle transmission Mueller matrices, we determine the spectral variation in the fundamental optical properties circular birefringence and dichroism. (C) 2017 Elsevier Ltd. All rights reserved.
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| 2. |
- Bi, Shubo, et al.
(författare)
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Influence of no-core fiber on the focusing performance of an ultra-small gradient-index fiber probe
- 2018
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Ingår i: Optics and lasers in engineering. - : ELSEVIER SCI LTD. - 0143-8166 .- 1873-0302. ; 107, s. 46-53
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Tidskriftsartikel (refereegranskat)abstract
- The light-beam expansion effect of a no-core fiber on the focusing performance of an ultra-small gradient-index fiber probe is investigated with a view to optimizing the optical performance of such probes. By taking the variable relationship between the focusing performance (including the working distance and the focusing spot size) of the probe and the length of the no-core fiber as the criterion, the effective beam expansion length of the no-core fiber in the ultra-small gradient-index fiber probe is calculated based on the basic properties of the Gaussian beam. Verification and analysis are done by numerical calculations and experimental measurements, respectively. The obtained results show that the working distance of an ultra-small gradient-index fiber probe can be increased effectively by adding a no-core fiber; however, this will lead to increasing the focusing spot size. For the parameters of the fiber probe studied here, the effective beam expansion length of the no-core fiber spacer is less than 0.357 mm. (C) 2018 Elsevier Ltd. All rights reserved.
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| 3. |
- Chen, Dingfu, et al.
(författare)
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Measurement of High Numerical Aperture Cylindrical Surface with Iterative Stitching Algorithm
- 2018
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Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 8:11
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Tidskriftsartikel (refereegranskat)abstract
- There are some limitations in null test measurements in stitching interferometry. In order to meet the null test conditions, the moving distance between the sub-apertures often deviates from the theoretical preset distance, which leads to a position deviation of sub-apertures when measured. To overcome this problem, an algorithm for data processing is proposed in this paper. An optimal estimation of the deviation between sub-apertures is used to update their positions, and then a new overlapped region is obtained and again optimized. This process is repeated until the algorithm converges to an acceptable tolerance, and finally exact stitching is realized. A cylindrical lens was taken as an object for experimental examination of the proposed method. The obtained results demonstrate the validity, reliability, and feasibility of our iterative stitching algorithm.
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| 4. |
- Hsiao, Ching-Lien, et al.
(författare)
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Curved-Lattice Epitaxial Growth of InxAl1-xN Nanospirals with Tailored Chirality
- 2015
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 15:1, s. 294-300
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Tidskriftsartikel (refereegranskat)abstract
- Chirality, tailored by external morphology and internal composition, has been realized by controlled curved-lattice epitaxial growth (CLEG) of uniform coatings of single-crystalline InxAl1-xN nanospirals. The nanospirals are formed by sequentially stacking segments of curved nanorods on top of each other, where each segment is incrementally rotated around the spiral axis. By controlling the growth rate, segment length, rotation direction, and incremental rotation angle, spirals are tailored to predetermined handedness, pitch, and height. The curved morphology of the segments is a result of a lateral compositional gradient across the segments while maintaining a preferred crystallographic growth direction, implying a lateral gradient in optical properties as well. Left- and right-handed nanospirals, tailored with 5 periods of 200 nm pitch, as confirmed by scanning electron microscopy, exhibit uniform spiral diameters of ~80 nm (local segment diameters of ~60 nm) with tapered hexagonal tips. High resolution electron microscopy, in combination with nanoprobe energy dispersive X-ray spectroscopy and valence electron energy loss spectroscopy, show that individual nanospirals consist of an In-rich core with ~15 nm-diameter hexagonal cross-section, comprised of curved basal planes. The core is surrounded by an Al-rich shell with a thickness asymmetry spiraling along the core. The ensemble nanospirals, across the 1 cm2 wafers, show high in-plane ordering with respect to shape, crystalline orientation, and direction of compositional gradient. Mueller matrix spectroscopic ellipsometry shows that the tailored chirality is manifested in the polarization state of light reflected off the CLEG nanospiral-coated wafers. In that, the polarization state is shown to be dependent on the handedness of the nanospirals and the wavelength of the incident light in the ultraviolet-visible region.
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| 5. |
- Patra, Hirak Kumar, et al.
(författare)
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Switchable label free apta-nanosensor: In situ biopsy?
- 2016
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Ingår i: <em>Biosensors 2016 – The World Congress on Biosensors</em>, Gothenburg, Sweden, 25-27 May 2016. - : Elsevier.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 6. |
- Sun, Tao, et al.
(författare)
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Algorithm for Surfaces Profiles and Thickness Variation Measurement of a Transparent Plate Using a Fizeau Interferometer with Wavelength Tuning
- 2019
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Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 9:11
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Tidskriftsartikel (refereegranskat)abstract
- An interferogram obtained from a transparent plate contains information on the profiles of both surfaces and on the thickness variation. The present work is devoted to the processing of interferograms of this type. The processing technique is based on a 36-step algorithm developed by the authors for characterization of transparent plates having approximately equal reflections from both sides. The algorithm utilizes weighted multi-step phase shifting that enables one not only separately to extract the front and rear surface profiles together with the thickness variation of the tested plate but also to suppress the coupling errors between the higher harmonics and phase-shift deviation. The proposed measuring method was studied on a wavelength tunable Fizeau interferometer. The tested sample had an optical thickness and surface profile deviations equal to 0.51 µm, 1.38 µm and 0.89 µm, respectively. According to the results obtained using 10 repeated measurements, the root mean square (RMS) errors for determining both surface profiles did not exceed 1.5 nm. Experimental results show that the setup and presented 36-step algorithm are suitable for the measurement of a transparent plate of arbitrary thickness.
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| 7. |
- Sun, Tao, et al.
(författare)
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Calibration of Tunable Diode Laser Wavelength Based on Energy Centrobaric Correction Method for Discrete Spectrum
- 2018
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Ingår i: SIXTH INTERNATIONAL CONFERENCE ON OPTICAL AND PHOTONIC ENGINEERING (ICOPEN 2018). - : SPIE-INT SOC OPTICAL ENGINEERING. - 9781510622579
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Konferensbidrag (refereegranskat)abstract
- The resolution of wavelength scanning of diode laser can influence the performance of interferometer mostly. In this article, we propose a method to improve the precision of wavelength calibration by using the theory of energy centrobaric correction for discrete spectrum. An optical wedge whose angle of tilt was known has been set in the optical system to measure the series of wavelength on time using a 2D Fourier Transfer (FT) of the interferograms generated by both surfaces of optical wedge. An energy centrobaric correction method is also put forward to evaluate the distribution of frequency and phase of fringe pattern generated by front and rear surface of optical wedge. The results of simulation and experiment show that the error of wavelength calibration reach to 0.01pm by correlating the distribution of frequency and phase of interferograms. The benefit is that the precision of wavelength of diode laser is improved significantly with a higher signal-to-noise ratio. This method can used to any tunable diode laser wavelength to improve the precision of measurement due to its simplicity and practicability.
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| 8. |
- Sun, Tao, et al.
(författare)
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Determination of surface profiles of transparent plates by means of laser interferometry with wavelength tuning
- 2019
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Ingår i: Optics and lasers in engineering. - : ELSEVIER SCI LTD. - 0143-8166 .- 1873-0302. ; 115, s. 59-66
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Tidskriftsartikel (refereegranskat)abstract
- An interferogram obtained from a transparent plate contains information about the profiles of both surfaces of the plate. This information can be extracted by processing fringe patterns measured at different wavelengths. The conventional Fourier analysis applied to solve such problems for a set of a restricted number of the fringe patterns is quite sensitive to the error of detuning the wavelength shifting and suffers from fringe patterns interference noise. This study proposes a method for finding surface profiles of a transparent plate using a series of fringe patterns obtained at different phase shifts caused by wavelength changes. The data treatment is based on the analytical approach for describing spatial distributions of irradiance in interference patterns. The results show that the proposed method is feasible. The experimental setup used herein was a Fizeau interferometer with tunable wavelength laser. A glass plate approximately 1 cm thick was as the test sample. According to the obtained results, the root mean square (RMS) errors for determining both surface profiles did not exceed 2.3 nm.
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| 9. |
- Valyukh, Sergiy, et al.
(författare)
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Assessment of minimum permissible geometrical parameters of a near-to-eye display
- 2015
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Ingår i: Applied Optics. - : Optical Society of America. - 1559-128X .- 2155-3165. ; 54:21, s. 6526-6533
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Tidskriftsartikel (refereegranskat)abstract
- Light weight and small dimensions are some of the most important characteristics of near-to-eye displays (NEDs). These displays consist of two basic parts: a microdisplay for generating an image and supplementary optics in order to see the image. Nowadays, the pixel size of microdisplays may be less than 4 mu m, which makes the supplementary optics the major factor in defining restrictions on a NED dimensions or at least on the distance between the microdisplay and the eye. The goal of the present work is to find answers to the following two questions: how small this distance can be in principle and what is the microdisplay maximum resolution that stays effective to see through the supplementary optics placed in immediate vicinity of the eye. To explore the first question, we consider an aberration-free magnifier, which is the initial stage in elaboration of a real optical system. In this case, the paraxial approximation and the transfer matrix method are ideal tools for simulation of light propagation from the microdisplay through the magnifier and the human eyes optical system to the retina. The human eye is considered according to the Gullstrand model. Parameters of the magnifier, its location with respect to the eye and the microdisplay, and the depth of field, which can be interpreted as the tolerance of the microdisplay position, are determined and discussed. The second question related to the microdisplay maximum resolution is investigated by using the principles of wave optics. (C) 2015 Optical Society of America
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| 10. |
- Valyukh, Sergiy, et al.
(författare)
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Bragg reflection from periodic helicoidal media with laterally graded refractive index
- 2017
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Ingår i: Optical materials (Amsterdam). - : ELSEVIER SCIENCE BV. - 0925-3467 .- 1873-1252. ; 72, s. 334-340
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Tidskriftsartikel (refereegranskat)abstract
- Light interaction with a columnar structure of InxAl1-xN where each column is a layered periodic helical medium with laterally graded refractive index is considered. It is demonstrated that such a columnar structure can be presented as a stack of layers with a gradient of the refractive index. To calculate reflectance in the proposed model, the 2 x 2 characteristic matrix method adopted for a gradient index medium was applied. The influence of the refractive indices (including absorption), parameters of the twisting, and thickness of the periodic structure on reflectance is studied. Cases of normal and oblique incident light are considered. The presented medium is a one-dimensional photonic crystal that can be utilized in many devices for light manipulation. (C) 2017 Published by Elsevier B.V.
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| 11. |
- Valyukh, Sergiy, et al.
(författare)
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Inline Quality Control of Liquid Crystal Cells
- 2015
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Ingår i: IEEE/OSA Journal of Display Technology. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1551-319X .- 1558-9323. ; 11:12, s. 1042-1047
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Tidskriftsartikel (refereegranskat)abstract
- Inline quality control of liquid crystal (LC) cells is usually associated with a real-time noncontact characterization of moved LC cells. Such a characterization enables inspection of the products quality and helps to find in time defects. In the paper, we analyze an approach for fast evaluation of LC cell gap uniformity. The approach is based on detecting interference patterns formed by the quasi-monochromatic light reflected from a tested LC cell. To speed up the data treatment, a simple analytic expression describing the intensity of light interacting with the multilayered structure of an LC cell is derived. The results of the simplified model are compared with rigorous simulations. Two experimental setups are discussed. A CCD camera is used for detecting the interference patterns.
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| 12. |
- Valyukh, Sergiy, et al.
(författare)
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Modeling of light interaction with exoskeletons of scarab beetles
- 2017
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Ingår i: Applied Optics. - : OPTICAL SOC AMER. - 1559-128X .- 2155-3165. ; 56:9, s. 2510-2516
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Tidskriftsartikel (refereegranskat)abstract
- Some beetles of the family Scarabaeidae produce brilliant metallic-looking colors by their pure dielectric exoskeletons and reflect light with a high degree of circular polarization. In the present work, we discuss three models for simultaneously describing scattering, spectral, and polarization characteristics of scarab beetles. Each model consists of three slabs: an outer thin epicuticle, an exocuticle having a helicoidal structure, and a thick uniform slightly absorbing endocuticle. Scattering features are defined by rough interfaces of the epicuticle and/or nonuniformities of the exocuticle. As an example, a slightly modified model of an earlier study of Chrysina aurata is considered. The modification is aimed at including surface and volume nonuniformities that affect not only spectral and polarization properties but also scattering. Another example of using the proposed models is based on the analysis of image formations of a specimen of the species Mimela chinensis, which was studied in a polarizing microscope at different magnifications. The results show that the proposed models can be applied for explanation of light interaction with the exoskeletons of scarab beetles. (C) 2017 Optical Society of America
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| 13. |
- Valyukh, Sergiy, et al.
(författare)
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Simulation of light scattering from exoskeletons of scarab beetles
- 2016
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Ingår i: Optics Express. - : OPTICAL SOC AMER. - 1094-4087. ; 24:6, s. 5794-5808
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Tidskriftsartikel (refereegranskat)abstract
- An approach for simulation of light scattering from beetles exhibiting structural colors originating from periodic helicoidal structures is presented. Slight irregularities of the periodic structure in the exoskeleton of the beetles are considered as a major cause of light scattering. Two sources of scattering are taken into account: surface roughness and volume non-uniformity. The Kirchhoff approximation is applied to simulate the effect of surface roughness. To describe volume non-uniformity, the whole structure is modeled as a set of domains distributed in space in different orientations. Each domain is modeled as an ideal uniformly twisted uniaxial medium and differs from each other by the pitch. Distributions of the domain parameters are assumed to be Gaussian. The analysis is performed using the Mueller matrix formalism which, in addition to spectral and spatial characteristics, also provides polarization properties of the scattered light. (C) 2016 Optical Society of America
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| 14. |
- Zeng, Zhenxiang, et al.
(författare)
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Full-color holographic display with increased-viewing-angle
- 2017
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Ingår i: Applied Optics. - : OPTICAL SOC AMER. - 1559-128X .- 2155-3165. ; 56:13, s. F112-F120
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Tidskriftsartikel (refereegranskat)abstract
- Among the important features of holographic displays are the wide viewing angles and the full color of the reconstructed images. The present work focuses on achievement of both features. We propose an increased-viewing-angle full-color holographic display using two tiled phase-only spatial light modulators (SLMs), a 4f concave mirrors system, and a temporal-spatial multiplexing method. The 4f optical system consists of two concave mirrors and serves to increase the viewing angle. A temporal-spatial multiplexing synchronization control (TSMSC) method is developed to achieve a full-color image and to remove the color crosstalk of the image. We calculate RGB phase-only holograms of a computer-generated color pyramid by using a slice-based Fresnel diffraction algorithm. The experimental results indicate that the proposed display system is feasible to reconstruct a full-color holographic 3D image with a viewing angle of 12.8 degrees, which is about 3.8 times wider than the viewing angle formed by a single SLM. (C) 2017 Optical Society of America
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