Optical fiber interferometer could achieve various dynamic measurements by transforming phase change into intensity change. In this paper, a novel Michelson interferometer (MI) based on two ...polarization beam splitters (PBSs) is proposed. Two thirds of Rayleigh backscattering (RB) is separated from the signal light by using PBS and Faraday rotating mirror (FRM) due to the difference polarization properties between RB and signal light in optical fibers. And the signal-to-noise ratio (SNR) of system has been significantly improved. Within the detection range of 50 km, the localization experiments on this new interferometer show that the SNR is increased by 6.69 dB compared with traditional MI on the condition of 500 kHz sampling rate. And the positioning accuracy can achieve ±100 m in the first-order null-frequency. The sensing distance also increases from 36.17 km to 49.42 km with a SNR of 15 dB. This proposed sensing system exhibits high sensitivity in the low frequency region, which is of great importance for long-distance buried optical cable detection and location.
Since infrared reflectography was first applied in the 1960s to visualize the underdrawings of ancient paintings, several devices and scanning techniques were successfully proposed both as prototypes ...and commercial instruments. In fact, because of the sensors' small dimension, typically ranging from 0.1 to 0.3 megapixels, scanning is always required. Point, line, and image scanners are all viable options to obtain an infrared image of the painting with adequate spatial resolution. This paper presents a newly developed, tailormade scanning system based on an InGaAs camera equipped with a catadioptric long-focus lens in a fixed position, enabling all movements to occur by means of a rotating mirror and precision step motors. Given the specific design of this system, as the mirror rotates, refocus of the lens is necessary and it is made possible by an autofocus system involving a laser distance meter and a motorized lens. The system proved to be lightweight, low cost, easily portable, and suitable for the examination of large-scale painting surfaces by providing high-resolution reflectograms. Furthermore, high-resolution images at different wavelengths can be obtained using band-pass filters. The in-situ analysis of a 16th-century panel painting is also discussed as a representative case study to demonstrate the effectiveness and reliability of the system described herein.
Optical fiber sensors are polarization sensitive and generally affected by polarization fading. This paper contributes to the optimal choice of polarization fading suppression methods for different ...optical fiber sensors, by means of comparative analysis of the mechanism of polarization fading, the strategy of polarization state control, and the applicability of suppression methods. The comparison results show that the polarization diversity receiving method is suitable for remote multi-channels optical fiber sensing system. The polarization orthogonal pulse pair method is only suitable for optical fiber sensing systems based on the backward scattering light. Meanwhile, the Faraday rotating mirror method is only suitable for optical fiber sensing systems based on the forward light interference. The polarization pulse coding method is suitable for sensing systems with high sensitivity and stability requirements. The polarization control method may increase the control complexity of sensing system for simultaneous variation of multiple polarization states. The full and partial polarization-maintaining fiber methods can be used to keep the polarization state of sensing light along the optical fiber, but the additional system cost limits the application. The polarization scrambler method is currently only available for sensing systems based on Brillouin scattering light. This paper provides a reference for the feasible selection of polarization fading suppression schemes for different optical fiber sensing systems.
Generation of entanglement between macroscale mechanical oscillators is challenging yet important for future quantum technologies. Here, the possibility of creating a steady‐state entanglement ...between two rotating mirrors in a Laguerre–Gaussian (LG) rotational‐cavity optomechanical system by placing an especially tuned degenerate optical parametric amplifier (OPA) inside the cavity is theoretically explored. In the resolved‐sideband regime, a LG cavity mode is driven by a Gaussian laser beam tuned to the first lower mechanical sideband. The Duan quantity and the logarithmic negativity is used to study the stationary entanglement between two rotating mirrors. The influence of the parametric gain and phase of the OPA, the input laser power, the temperature of the environment, and the topological charge of the LG cavity mode on the mechanical entanglement are investigated. The achievable maximal degree of entanglement is limited by the parametric gain of the OPA.
Generation of entanglement between macroscale mechanical oscillators is challenging yet important for future quantum technologies. Here, the possibility of creating a steady‐state entanglement between two rotating mirrors in a Laguerre‐Gaussian rotational‐cavity optomechanical system by placing an especially tuned degenerate optical parametric amplifier inside the cavity is theoretically explored.
Three- to 4-month-old female and male human infants were administered a two-dimensional mental-rotation task similar to those given to older children and adults. Infants were familiarized with the ...number 1 (or its mirror image) in seven different rotations between 0° and 360°, and then preference-tested with a novel rotation of the familiar stimulus paired with its mirror image. Male infants displayed a novelty preference for the mirror-image stimulus over the novel rotation of the familiar stimulus, whereas females divided attention between the two test stimuli. The results point toward an early emergence of a sex difference in mental rotation.
Abstract
This study aims to examine the influence law of polyhedron structure on the spatial mechanical properties of ultra-high-speed rotating mirrors. To this end, polyhedral beryllium alloy ...rotating mirrors are investigated on the basis of elastoplastic theory and finite element method. The maximum stress is located at the end position of the contact between the shaft and the mirror body. Stress increases with the number of mirror faces. The different structures have a negative stress gradient. The structural strength of rotating mirror is affected by the strength of the mirror body material in high-speed rotation of the tensile force of centrifugal force. The lateral deformation of the mirror surface is caused by the combined effect of compression of centrifugal force generated by the material of sharp-corner and the tretching of tensile force caused by the material at the centre of the mirror at high-speed rotation. The amount of mirror surface deformation is not proportional to the number of faces. The rotating mirror with iso-quadrangular structure has the best lateral deformation effect. This research provides a theoretical basis for the research and design of rotating mirrors with high potential value.
In the limit of sufficiently fast rotation, rotating mirror traps are known to be stable against the loss-cone modes associated with conventional (non-rotating) mirrors. This paper calculates how ...quickly a mirror configuration must rotate in order for several of these modes to be stabilized (in particular, the high-frequency convective loss cone, drift cyclotron loss cone and Dory–Guest–Harris modes). Commonalities in the stabilization conditions for these modes then motivate a modified formulation of the Gardner free energy and diffusively accessible free energy to be used for systems in which the important modes have wavevectors that are orthogonal or nearly orthogonal to the magnetic field, as well as a modification to include the effects of a loss region in phase space.
We report the experimental observations of Bell inequality violations (BIV) in entangled photons causally separated by a rotating mirror. A Foucault mirror gating geometry is used to causally isolate ...the entangled photon source and detectors. We report an observed BIV of CHSH-S=2.30±0.07>2.00. This result rules out theories that explain correlations with traveling communication between source and detectors, including super-luminal and instantaneous communication.
Flow evolution over helicopter rotors, wind turbine blades, and insect wings are unsteady, three-dimensional (3D), and influenced by phenomena unique to the rotating frame of reference (FoR), e.g., ...Coriolis and centrifugal forces. Conventional 3D-PIV techniques are unable to fully characterize these rotating FoR physics, since the measurements are limited to a fixed FoR of a relatively small volume through which the rotor blade or wing traverses intermittently. In this paper, a new “Rotating Three-Dimensional Velocimetry (R3DV)” technique is proposed to address these gaps. R3DV consists of 3D measurements made with a single stationary plenoptic camera in combination with a hub-mounted mirror that aligns the camera’s field of view with a rotating wing. In post-processing R3DV data, a rotational volumetric calibration method is developed to account for image acquisition through a rotating mirror. Rotating FoR volumes are then reconstructed using the Multiplicative Algebraic Reconstruction Technique (MART) algorithm with the adapted calibration scheme and subsequently cross-correlated to derive a 3D velocity field. R3DV was experimentally demonstrated in a study of 3D unsteady flow over an impulsively rotated flat-plate wing. Prominent flow features like the formation and shedding of the primary and secondary leading-edge vortices (LEVs) were observed, which corroborate well with the existing literature on rotating wings. The time-resolved variation of LEV velocity profiles and circulation with azimuthal angle exhibited expected trends. The ability to quantify 3D and time-resolved velocity fields in the rotating FoR demonstrates the feasibility of adopting R3DV as a technique to investigate rotating flows.
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