Hasil untuk "Applied optics. Photonics"

Xiao-Li Ma, Han-Le Zhang, Bo Hu et al.

Large depth of field (DOF) is a core pursuit in integral imaging (InIm). In this paper, we propose a DOF-enhanced InIm display system comprising a transmissive mirror device (TMD), a semi-transparent mirror (STM), two 2D displays, and a micro-lens array (MLA). The two 2D displays pre-render two sets of elemental image arrays (EIAs), each corresponding to a distinct depth plane. The STM spatially coaxializes the two EIAs emitted by the two 2D displays. At the same time, the TMD collaborates with the STM to adjust the effective projection distances of the coaxialized EIAs onto the MLA to different values. The MLA couples with the two EIAs projected at different effective distances, enabling the reconstruction of three-dimensional (3D) images at two separate central depth planes (CDPs). This system solves the narrow DOF issue in conventional InIm displays by reconstructing 3D images at two separate CDPs, thus enhancing the DOF. Notably, the proposed system achieves an approximate two-fold increase in DOF compared to a conventional one. A prototype of the DOF-enhanced InIm display system is constructed, and experimental results verify its feasibility.

J.-E. Heitz, M. Koehl

As part of the Interreg VI Ch&acirc;teaux rh&eacute;nans &ndash; Burgen Am Oberrhein project, INSA Strasbourg is carrying out heritage conservation work on several castles on the Rhine plain. This work consists of 3D topographic surveys of the sites to crystallize them at a given time. Then, in a second phase, this work focuses on the modelling of 3D historical reconstructions of the sites. This challenge is carried out in collaboration with specialised archaeologists, to bring these castles back to life. The objective of this work is to promote the Rhineland castle heritage through digital technology. To increase the influence of these 4D models integrating different temporalities, a Unity game that can be used in a virtual reality cave has been created. Indeed, this method of valuation increases the public's immersion in the model and allows them to project themselves into the reality of the field. The methodology involves converting the models made with <em>Blender</em> to <em>Unity</em>, then creating a game with <em>Unity</em>. Finally, a self-guided game of a set of castles modelled at different historical periods is proposed. This game, focused on the player's immersion, gives access to menus allowing to choose the castle or the desired historical era. It also provides a range of fun tools allowing the player to move objects and take photos. It is also intended to be educational, by offering informative bubbles or interactions with NPCs, while roaming the castles to the rhythm of medieval music. VR is used here as a fun way to enhance the project's digital content in a more immersive form to the public.

Artem B. Solomashenko, Olga L. Afanaseva, Maria V. Shishova et al.

This review considers the modern industrial applications of augmented reality headsets. It draws upon a synthesis of information from open sources and press releases of companies, as well as the first-hand experiences of industry representatives. Furthermore, the research incorporates insights from both profile events and in-depth discussions with skilled professionals. A specific focus is placed on the ergonomic characteristics of headsets: image quality, user-friendliness, etc. To provide an objective evaluation of the various headsets, a metric has been proposed which is dependent on the specific application case. This enables a comprehensive comparison of the various devices in terms of their quantitative characteristics, which is of particular importance for the formation of a rapidly developing industry.

J. Tian, J. Tian, D. Panangian et al.

Accurate delineation of individual tree crowns (ITC) enables a better understanding of tree-level growth dynamics and evaluating tree vitality. In recent year, researches have introduced deep learning techniques in this field. However, the precise segmentation relies on high quality annotated dataset and test images with limited domain gaps between the training data. Under the framework of the Helmholtz project, panchromatic airborne images are captured over a mixed European forest. In this research, we adopt a UAV benchmark dataset as training data. To close the domain gaps, a deep learning based colorization step is added, for which two deep learning frameworks are compared to achieve an improved ITC delineation result in a dense forest area.

T. Faitli, H. Hyyti, J. Hyyppä et al.

This paper addresses how to utilize multiple spinning lidar sensors for real-time applications. Especially how to derive back the problem to having only a single lidar input, to which there are countless available algorithms solving odometry, mapping, object detection and tracking and many other tasks. We provide a strategy that can be implemented to most if not all spinning lidars on the market. Instead of traditional data batching that accumulates data packets based on the spinning angle, we propose batching based on the sampling time, which also enable us to ensure strict time alignment within the multiple lidar sources. In order to demonstrate our batching strategy, we provide a case study where we evaluated a SLAM algorithm with a single and a dual-lidar setup. Our batching algorithm enabled us to use the SLAM algorithm that was previously designed for a single spinning lidar without any additional change, while it showcased benefits, especially in stability due to the larger field of view and reduced occlusion.

Christopher Perrella, Kishan Dholakia

Abstract An original form of photonic force microscope has been developed. Operating with a trapped lanthanide-doped crystal of nanometric dimensions, a minimum detected force of the order of 110 aN and a force sensitivity down to 1.8 fN/ $$\sqrt{{\rm{Hz}}}$$ Hz have been realised. This opens up new prospects for force sensing in the physical sciences.

Yuri Aleksandrovich Konstantinov, Artem Timofeevich Turov, Konstantin Pavlovich Latkin et al.

This work is devoted to the scientific and technical aspects of individual stages of active optical fibers preforms’ optical-geometric parameters metrological control. The concept of a system presented makes it possible to carry out a study of a rare earth element distribution in the preform of an active optical fiber and to monitor geometric parameters, and also to study the evolution of the refractive index profile along the length of the sample at a qualitative level. As far as it is known, it is the first description of the preform optical, geometric, and luminescent properties measurement within a single automated laboratory bench. Also, the novelty of the approach lies in the fact that the study of the refractive index profile variation along the length of the preform is, for the first time, conducted using the “dry” method, that is, without immersing the sample in synthetic oil, which makes the process less labor-intensive and safer.

GE Minghao, ZHAO Laiding, ZHANG Gengxin

The single-satellite multi-beam interference source localization method requires more than three co-frequency beams to receive the interference source signal to achieve positioning. Due to the limited number of co-frequency beams and the randomness of the location of the interference source, it is usually that the co-frequency beams can receive the interference source signal less than three, or low receiving gain, which may affect the positioning accuracy.【Objective】In order to solve the problem of positioning with only two available beams and further improve the positioning accuracy of interference sources, a dual-satellite joint positioning model based on multi-beam antenna and Time Difference of Arrival (TDOA) technology is proposed through adjacent stars and main stars.【Methods】In this paper, the feasibility of the model is proved by establishing the dual-satellite joint positioning model and the positioning equations in parallel. At the same time, based on Geometric Dilution of Precision (GDOP), the positioning error of the positioning model is analyzed from four aspects: receiving gain error, beam pointing error, arrival time difference error and position prediction error.【Results】The simulation results show that the positioning accuracy of the dual-satellite joint positioning method based on multi-beam antenna and TDOA technology is obviously better than the traditional single-satellite multi-beam positioning method.【Conclusion】The dual-satellite joint positioning method based on multi-beam antenna and TDOA technology makes use of the advantage that TDOA has less influence on positioning accuracy. Therefore, it replaces part of the beam to participate in satellite positioning, which not only reduces the demand for the number of positioning beams, but also reduces the error of measurement gain and the error of beam pointing with improved positioning accuracy and the reliability. The simulation results indicate that the proposed method is a better positioning method than single-satellite multi-beam positioning.

Jing Yu, Wei Zhou, Dedan Mou et al.

Cesium copper iodine perovskite is widely studied for applications in X-ray imaging and anti-counterfeiting fields based on its excellent photovoltaic properties. Uniquely, Cs3Cu2I5 undergoes a reversible phase transition to CsCu2I3 when induced by humidity, a phenomenon that is utilized in fluorescent anti-counterfeiting application. However, there is no relevant proof for the phase transition of CsCu2I3 upon humidity, which leads to an incomplete explanation of the water-induced phase transition of Cs3Cu2I5. Here, we illustrate the water-induced phase transition events of Cs3Cu2I5 and CsCu2I3 crystals that were made utilizing a straightforward anti-solvent approach. Interestingly, Cs3Cu2I5 can undergo a reversible phase transition based on humidity exposure and removal, whereas CsCu2I3 undergoes immediate phase decomposition and fluorescence burst upon humidity exposure, and recrystallization to low-formation-energy Cs3Cu2I5 is accompanied by fluorescence recurrence after humidity evaporation. Furthermore, Cs3Cu2I5 and CsCu2I3 crystals exhibit a fascinating X-ray light yield and a high spatial resolution of 16.6 and 12.5 lp mm−1, respectively. As a result, this research adds to our understanding of the phase transition between Cs3Cu2I5 and CsCu2I3 and also provides new candidates for advanced fluorescence anti-counterfeiting techniques and X-ray imaging scintillators.

Christopher Yeung, Ju-Ming Tsai, Brian King et al.

Explainable machine learning algorithms were applied to convolutional neural networks to reveal deeper insights into the properties of metamaterials, demonstrating new avenues for physics discovery and device optimization in optics and photonics.

A. Fleisher, K. Chan, M. Ferreira et al.

This joint feature issue of Optics Express and Applied Optics highlights contributions from authors who presented their latest research at the OSA Optical Sensors and Sensing Congress, held in San Jose, California, USA from 25-27 June 2019. The joint feature issue comprises 6 contributed papers, which expand upon their respective conference proceedings. The published papers introduced here cover a range of timely research topics in optics and photonics for active open-path sensing, radiometry, and adaptive optics and fiber devices.

S. Gorb, E. Gorb

A. Alhasan, T. Ali

A. Fleisher, P. Bermel, F. Harren et al.

This joint feature issue of Optics Express and Applied Optics highlights contributions from authors who presented their latest research at the OSA Light, Energy and the Environment Congress, held in Sentosa Island, Singapore from 5 to 8 November 2018. The joint feature issue comprises 11 contributed papers, which expand upon their respective conference proceedings. The published papers introduced here cover a broad range of timely research topics in optics and photonics for lighting and illumination, solar energy, hyperspectral imaging, and environmental sensing.

Wei He, Lianqing Zhu, Wen Zhang et al.

We propose a point-by-point inscription method for fiber Bragg grating (FBG) fabrication using a femtosecond pulsed laser focused through a fiber polyimide coating, realizing a 2-<italic>&#x03BC;</italic>m-wavelength-band FBG. A femtosecond laser acts as the inscription laser, focused by a 63&#x00D7; oil lens. A first-order FBG was fabricated with a grating interval of 700&#x00A0;nm. The 15-<italic>&#x03BC;</italic>W pulsed laser was focused directly on the fiber core through the polyimide coating and cladding. A first-order FBG for 2004.8-nm light with more than 56&#x0025; reflectances was fabricated. High wavelength sensitivity and linearity of the FBG were demonstrated by temperature and strain-sensing testing. The first-order FBG of 2004.8 and 2000.2&#x00A0;nm resonant wavelengths could be realized simultaneously through parallel inscription method in 3000&#x00A0;<italic>&#x03BC;</italic>m long grating area.

A. M. G. Tommaselli, M. B. Campos, L. F. Castanheiro et al.

Low cost imaging and positioning sensors are opening new frontiers for applications in near real-time Photogrammetry. Omnidirectional cameras acquiring images with 360&deg; coverage, when combined with information coming from GNSS (Global Navigation Satellite Systems) and IMU (Inertial Measurement Unit), can efficiently estimate orientation and object space structure. However, several challenges remain in the use of low-cost sensors and image observations acquired by sensors with non-perspective inner geometry. The accuracy of the measurement using low-cost sensors is affected by different sources of errors and sensor stability. Microelectromechanical systems (MEMS) present a large gap between predicted and actual accuracy. This work presents a study on the performance of an integrated sensor orientation approach to estimate sensor orientation and 3D sparse point cloud, using an incremental bundle adjustment strategy and data coming from a low-cost portable mobile terrestrial system composed by off-theshelf navigation systems and a poly-dioptric system (Ricoh Theta S). Experiments were performed in an outdoor area (sidewalk), achieving a trajectory positional accuracy of 0.33&thinsp;m and a meter level 3D reconstruction.

Burak Gerislioglu, Arash Ahmadivand

Here, we study the possibility of exquisitely selective harmonic generation based on the concept of charge transfer plasmons (CTPs) in bridged nanoparticle assemblies. By choosing plasmonic dimer nanoantenna, as a fundamental member of the nanocluster family, and bridging the capacitive gap space between the proximal nanoparticles with an optothermally controllable substance, we judiciously showed that variations in the generation of third harmonic light in the visible regime can be possible by considering distinct states of the functional bridge. To this end, the conductive connection between the nanoparticles is mediated with Ge₂Sb₂Te₅ (GST) with inherently opposite optical and electrical properties below (dielectric, amorphous state) and above 477 &#176;C (conductive, crystalline state). This helped to actively control the transition of charges across the bridge and thereby control the excitation of CTP resonances and provide a switching feature between dipolar and CTP modes. This versatile approach also allowed for production of the intended harmonic signal at different wavelengths depending on the conductivity of the interparticle nanojunction.

A. Fleisher, P. Bermel, Frans J. M. Harren et al.

This joint feature issue of Optics Express and Applied Optics highlights contributions from authors who presented their latest research at the OSA Light, Energy and the Environment Congress, held in Sentosa Island, Singapore from 5-8 November 2018. The joint feature issue comprises 11 contributed papers, which expand upon their respective conference proceedings. The published papers introduced here cover a broad range of timely research topics in optics and photonics for lighting and illumination, solar energy, hyperspectral imaging, and environmental sensing.

A. Fleisher, P. Bermel, F. Harren et al.

M. Mazilu, A. Demčenko, Rab Wilson et al.

Although the conservation of momentum is a fundamental law in physics, its constraints are not fulfilled for wave propagation at material boundaries, where incident waves give rise to evanescent field distributions. While nonlinear susceptibility tensor terms can provide solutions in the optical regime, this framework cannot be applied directly to acoustic waves. Now, by considering a complete representation of wave interactions and scattering at boundaries, we are able to show a generic formalism of sum-frequency mixing for the whole scattering field including all evanescent waves. This general case was studied analytically and verified both numerically and experimentally for ultrasonic waves, showing that considering evanescent waves leads to an anomalous nonlinear interaction which enhances sum-frequency generation. This new interpretation not only provides a deeper understanding of the momentum conservation laws in acoustics but also promises translation of this new understanding into optics and photonics, to enhance nonlinear interactions.