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1 – 10 of 120Laura D. Vallejo-Melgarejo, Ronald G. Reifenberger, Brittany A. Newell, Carlos A. Narváez-Tovar and José M. Garcia-Bravo
An Autodesk Ember three-dimensional (3D) printer was used to print optical components from Clear PR48 photocurable resin. The cured PR48 was characterized by the per cent of light…
Abstract
Purpose
An Autodesk Ember three-dimensional (3D) printer was used to print optical components from Clear PR48 photocurable resin. The cured PR48 was characterized by the per cent of light transmitted and the index of refraction, which was measured with a prism spectrometer. Lenses and diffraction gratings were also printed and characterized. The focal length of the printed lenses agreed with predictions based on the thin lens equation. The periodicity and effective slit width of the printed gratings were determined from both optical micrographs and fits to the Fraunhofer diffraction equation. This study aims to demonstrate the advantages offered by a layer-by-layer DLP printing process for the manufacture of optical components for use in the visible region of the electromagnetic spectrum.
Design/methodology/approach
A 3D printer was used to print both lenses and diffraction gratings from Standard Clear PR48 photocurable resin. The manufacturing process of the lenses and the diffraction gratings differ mainly in the printing angle with respect to the printer x-y-axes. The transmission diffraction gratings studied here were manufactured with nominal periodicities of 10, 25 and 50 µm. The aim of this study was to optically determine the effective values for the distance between slits, d, and the effective width of the slits, w, and to compare these values with the printed layer thickness.
Findings
The normalized diffraction patterns measured in this experiment for the printed gratings with layer thickness of 10, 25 and 50 µm are shown by the solid dots in Figures 8(a)-(c). Also shown as a red solid line are the fits to the experimental diffraction data. The effective values of d and w obtained from fitting the data are compared to the nominal layer thickness of the printed gratings. The effective distance between slits required to fit the diffraction patterns are well approximated by the printed layer thickness to within 14, 4 and 16 per cent for gratings with a nominal 10, 25 and 50 µm layer thickness, respectively.
Research limitations/implications
Chromatic aberration is present in all polymer lenses, and the authors have not attempted to characterize it in this study. These materials could be used for achromatic lenses if paired with a crown-type material in an achromatic doublet configuration, because this would correct the chromatic aberration issues. It is worthwhile to compare the per cent transmission in cured PR48 resin (approximately 80 per cent) to the percent transmission found in common optical materials like BK7 (approximately 92 per cent) over the visible region. The authors attribute the lower transmission in PR48 to a combination of surface scattering and increased absorption. At the present time, the authors do not know what fraction of the lower transmission is related to the surface quality resulting from sample polishing.
Practical implications
There are inherent limitations to the 3D manufacturing process that affect the performance of lenses. Approximations to a curved surface in the design software, the printing resolution of the Autodesk Ember printer and the anisotropy due to printing in layers are believed to be the main issues. The performance of the lenses is also affected by internal imperfections in the printed material, in particular the presence of bubbles and the inclusion of debris like dust or fibers suspended in air. In addition, the absorption of wavelengths in the blue/ultraviolet produces an undesirable yellowing in any printed part.
Originality/value
One of the most interesting results from this study was the manufacture of diffraction gratings using 3D printing. An analysis of the diffraction pattern produced by these printed gratings yielded estimates for the slit periodicity and effective slit width. These gratings are unique because the effective slit width fills the entire volume of the printed part. This aspect makes it possible to integrate two or more optical devices in a single printed part. For example, a lens combined with a diffraction grating now becomes possible.
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Gianluca Ruffato and Filippo Romanato
– The purpose of this paper is to simulate and analyze the excitation and propagation of surface plasmon polaritons (SPPs) on sinusoidal metallic gratings in conical mounting.
Abstract
Purpose
The purpose of this paper is to simulate and analyze the excitation and propagation of surface plasmon polaritons (SPPs) on sinusoidal metallic gratings in conical mounting.
Design/methodology/approach
Chandezon's method has been implemented in MATLAB environment in order to compute the optical response of metallic gratings illuminated under azimuthal rotation. The code allows describing the full optical features both in far- and near-field terms, and the performed analyses highlight the fundamental role of incident polarization on SPP excitation in the conical configuration.
Findings
Results of far-field polarization conversion and plasmonic near-field computation clearly show that azimuthally rotated metallic gratings can support propagating surface plasmon with generic polarization.
Originality/value
The recent papers experimentally demonstrated the benefits in sensitivity and the polarization phenomenology that are originated by an azimuthal rotation of the grating. In this work, numerical simulations confirm these experimental results and complete the analysis with a study of the excited SPP near-field on the metal surface.
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Z.W. Zhong and S.K. Nah
This paper reports on a study of the scanning electron microscope (SEM) Moiré method. Tests were carried out by rotating the specimen grating slightly with respect to the electron…
Abstract
This paper reports on a study of the scanning electron microscope (SEM) Moiré method. Tests were carried out by rotating the specimen grating slightly with respect to the electron scanning raster lines, to verify that the Moiré images captured were really due to the interference between specimen and reference gratings. The experimental results coincided well with the calculated theoretical values and with small measurement errors. Then, the shear strains experienced by the solder joints of a flip‐chip ball grid array specimen were investigated using the SEM Moiré method. The results were compared with those obtained using the optical Moiré method.
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Tae-Bong Lee and Min-Nyeon Kim
– The purpose of this paper is to analyze far and near field emitted field patterns through more exact calculation of the modes formed in finite periodic dielectric gratings.
Abstract
Purpose
The purpose of this paper is to analyze far and near field emitted field patterns through more exact calculation of the modes formed in finite periodic dielectric gratings.
Design/methodology/approach
For the mode calculation, equations are newly defined by applying vertical boundary condition on the assumption that transverse electric modes are generated in the structure. After finding modes, near field patterns are calculated using the wave number and coefficient of the mode.
Findings
Additionally, the results from these calculations are compared with that of the rigorous-coupled method. Finally, far field patterns are derived by applying fast Fourier transform to near field patterns and also compared with the results of rigorous-coupled method.
Research limitations/implications
For convenience of coordinate, we use rectangular coordinate, though the shape of radome is a hemisphere.
Practical implications
In this paper, the authors derive more exact near field patterns without the assumption of infiniteness so that these results can be used practically for a making real frequency-selective structure.
Originality/value
Conventional periodic finite dielectric gratings analysis has been done using Floquet–Bloch wave theory, coupled-mode, rigorous-coupled method which is based on the assumption of infiniteness of the structure.
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Shaoyi Xu, Fangfang Xing, Ruilin Wang, Wei Li, Yuqiao Wang and Xianghui Wang
At present, one of the key equipment in pillar industries is a large rotating machinery. Conducting regular health monitoring is important for ensuring safe operation of the large…
Abstract
Purpose
At present, one of the key equipment in pillar industries is a large rotating machinery. Conducting regular health monitoring is important for ensuring safe operation of the large rotating machinery. Because vibrations sensors play an important role in the workings of the rotating machinery, measuring its vibration signal is an important task in health monitoring. This paper aims to present these.
Design/methodology/approach
In this work, the contact vibration sensor and the non-contact vibration sensor have been discussed. These sensors consist of two types: the electric vibration sensor and the optical fiber vibration sensor. Their applications in the large rotating machinery for the purpose of health monitoring are summarized, and their advantages and disadvantages are also presented.
Findings
Compared with the electric vibration sensor, the optical fiber vibration sensor of large rotating machinery has unique advantages in health monitoring, such as provision of immunity against electromagnetic interference, requirement of less insulation and provision of long-distance signal transmission.
Originality/value
Both contact vibration sensor and non-contact vibration sensor have been discussed. Among them, the electric vibration sensor and the optical fiber vibration sensor are compared. Future research direction of the vibration sensors is presented.
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This paper presents a micrograting‐based force sensor integrated with a surface micromachined silicon‐nitride probe suitable for characterizing microsurgery force on a single cell…
Abstract
This paper presents a micrograting‐based force sensor integrated with a surface micromachined silicon‐nitride probe suitable for characterizing microsurgery force on a single cell or embryo. The probe is supported by springs of a known spring constant, and the surgical penetration force is determined from displacement measurements. The optical‐encoder force sensor exhibits configurable sensitivity and dynamic range, allowing monitoring over a wide range of forces. The periodicity of the encoder response can be used for calibration of the injector displacement and to obtain information about the localized elastic properties of the target. We used a force sensor with a measured spring constant of 1.85 N/m for penetration force measurements on Drosophila embryos, and found a penetration force of 52.5 μN (±13.2 percent) and a membrane displacement of 58 μm (±5.2 percent).
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Moiré fringe transducers have much potential — but they are being under‐utilised according to PA Technology. Sarah Gardner reports.
Optical fibre multiplexed sensors are used to make measurements at multiple, discrete locations, usually by sending optical signals between each measurement location and a…
Abstract
Optical fibre multiplexed sensors are used to make measurements at multiple, discrete locations, usually by sending optical signals between each measurement location and a conveniently positioned optical interrogation instrument. It is rapidly becoming practical to construct multiplexed optical fibre sensor arrays based on in‐fibre Bragg gratings. A Bragg grating can be produced in an optical fibre by writing a periodic variation in the refractive index of the fibre’s core along the axis, using ultra‐violet light. Multiplexing applications will appear ranging from the small scale, with only a few sensors, up to very large scales with hundreds of sensors.
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Abstract
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M.C. Hutley, R.F. Stevens and D.E. Putland
The use of optical fibres in sensors is opening up new possible applications for industrial measurement