Motion Of Mirror Research Articles

Research on the Image-Motion Compensation Technology of the Aerial Camera Based on the Multi-Dimensional Motion of the Secondary Mirror

Research on the Image-Motion Compensation Technology of the Aerial Camera Based on the Multi-Dimensional Motion of the Secondary Mirror

Research on Positioning Tracking Mode of Sports Rehabilitation Training Based on Self-Powered Sensor Based on Particle Swarm Optimization Algorithm

The theme of today’s world is peace and development. A stable external environment has made people’s average life expectancy gradually increased, and the world is rapidly aging. Aging has brought many problems, such as the increase in the number of patients with limb dysfunction due to various diseases, which has gradually increased the demand for rehabilitation training. With traditional rehabilitation training methods, the training scenes are single and boring, and patients are prone to resisting. This paper designs and implements a real-time rehabilitation training guidance system based on self-powered sensors for the rehabilitation training needs of stroke patients. The system uses self-powered sensors to collect human motion information in real time, and compares it with the key posture sequences in the standard motion library to obtain corresponding matching results and guide patients to perform correct rehabilitation training. Using the rotation quaternion of 25 bone points in the patient’s rehabilitation exercise to calculate and update the rotation quaternion of the corresponding bone point of the character model, the function of the character model to follow the patient’s mirror motion is realized. This allows patients to control the completion of their rehabilitation movements without the need for medical staff to accompany them. And the stability of the system is optimized based on the particle swarm optimization algorithm. After traversal optimization, the current sensitivity coefficient of the model is reduced by about 75% compared with that before the correction, indicating that the current stability of the model obtained at this time has been improved to a certain extent. However, in the regression model of the self-powered sensor established by the particle swarm optimization algorithm, its parameters are reduced by about 82% compared with those before the correction, which shows that the current stability of the model has been greatly improved at this time, and the operating current of the receiving loop has been greatly improved.

IR-finite thermal acceleration radiation

A charge accelerating in a straight line following the Schwarzschild–Planck moving mirror motion emits thermal radiation for a finite period. Such a mirror motion demonstrates quantum purity and serves as a direct analogy of a black hole with unitary evolution and complete evaporation. Extending the analog to classical electron motion, we derive the emission spectrum, power radiated, and finite total energy and particle count, with particular attention to the thermal radiation limit. This potentially opens the possibility of a laboratory analog of black hole evaporation.

Research on 2D Image Motion Compensation for a Wide-Field Scanning Imaging System with Moving Base

The wide-field imaging system carried on a high-altitude or near-space vehicle takes high-resolution images of the ground to measure and map targets. With the improvement of imaging resolution and measurement accuracy, the focal length of the wide-field imaging system is getting longer. The requirement for image motion compensation (IMC) accuracy is getting higher, and the influence of optical path coupling is increasing within the process of two-dimensional (2D) IMC. To further improve the IMC accuracy of the wide-field imaging system, an innovative IMC method is first proposed in this paper. The method is based on the 2D motion of the scanning platform and secondary mirror. Secondly, to solve the optical coupling problem in the process of 2D IMC, the coupling phenomenon is analyzed. The coupling relationships between 2D scanning motion, 2D secondary mirror motion and image motion is derived from the compensation process. A complete 2D IMC model is established, and a 2D IMC method, including an optical path decoupling correct regulator (ODCR), is designed. Finally, the method is verified in laboratory and field flight tests. The results show that the proposed method can effectively correct the coupling error of the optical path in the process of IMC and achieve high-resolution 2D IMC. When the scanning speed is 60°/s and the exposure time is 2 ms, the accuracy of the 2D IMC is up to 0.57pixels (RMS) in the pitch direction, and 0.46 pixels (RMS) in the roll direction.

Conceptual design and analysis of remote steering system for CFETR ECRH system

In order to optimize the operational safety and reliability of the upper launcher for the CFETR ECRH system, a design of the launcher based on the remote steering concept is currently being carried out for comparison with the front steering equivalent. This paper presents the remote steering system's conceptual design and simulation analysis. A Square Corrugated Waveguide (SCW) of 65 × 65 mm has been designed with an optimized length of 9.35 m. By changing the relative length of the waveguide, the transmission efficiency of the SCW is optimized within the range of steering angles ±12°. Different error factors are investigated in detail, and corresponding acceptable error ranges are provided. Considering these error factors and ignoring ohmic losses and thermal effects, the relative transmission efficiency of the SCW is estimated to be >98 % within the steering angle range. A matching steering unit for the SCW is designed, which consists of an ellipsoidal focusing mirror and a steerable flat mirror. The detailed design of the steerable mirror motion trajectory is presented. Also, the influence of the possible beam incident errors caused by the steering unit on the transmission efficiency is analyzed in detail.

Frequency chirped Fourier-Transform spectroscopy

Fast (sub-second) spectroscopy with high spectral resolution is of vital importance for revealing quantum chemistry kinetics of complex chemical and biological reactions. Fourier transform (FT) spectrometers can achieve high spectral resolution and operate at hundreds of ms time scales in rapid-scan mode. However, the linear translation of a scanning mirror imposes stringent time-resolution limitations to these systems, which makes simultaneous high spectral and temporal resolution very difficult. Here, we demonstrate an FT spectrometer whose operational principle is based on continuous rotational motion of the scanning mirror, effectively decoupling the spectral resolution from the temporal one. Furthermore, we show that such rotational FT spectrometer can perform Mid-IR dual-comb spectroscopy with a single comb source, since the Doppler-shifted version of the comb serves as the second comb. In our realization, we combine the advantages of dual-comb and FT spectroscopy using a single quantum cascade laser frequency comb emitting at 8.2 μm as a light source. Our technique does not require any diffractive or dispersive optical elements and hence preserve the Jacquinot’s-, Fellgett’s-, and Connes’-advantages of FT spectrometers. By integrating mulitple broadband sources, such system could pave the way for applications where high speed, large optical bandwidth, and high spectral resolution are desired.

Optomechanical sideband asymmetry explained by stochastic electrodynamics

Within the framework of stochastic electrodynamics we derive the noise spectrum of a laser beam reflected from a suspended mirror. The electromagnetic field follows Maxwell's equations and is described by a deterministic part that accounts for the laser field and a stochastic part that accounts for thermal and zero-point background fluctuations.Likewise, the mirror motion satisfies Newton's equation of motion and is composed of deterministic and stochastic parts, similar to a Langevin equation. We consider a photodetector that records the power of the field reflected from the mirror interfering with a frequency-shifted reference beam (heterodyne interferometry). We theoretically show that the power spectral density of the photodetector signal is composed of four parts: (i) a deterministic term with beat notes, (ii) shot noise, (iii) the actual heterodyne signal of the mirror motion and (iv) a cross term resulting from the correlation between measurement noise (shot noise) and backaction noise (radiation pressure shot noise). The latter gives rise to the Raman sideband asymmetry observed with ultracold atoms, cavity optomechanics and with levitated nanoparticles. Our classical theory fully reproduces experimental observations and agrees with the results obtained by a quantum theoretical treatment.

Particle acceleration and radiation reaction in a strongly magnetised rotating dipole

Context. Neutron stars are surrounded by ultra-relativistic particles efficiently accelerated by ultra-strong electromagnetic fields. These particles copiously emit high-energy photons through curvature, synchrotron and inverse Compton radiation. To date, however, no numerical simulations have been able to handle such extreme regimes of very high Lorentz factors and magnetic field strengths close to or even above the quantum critical limit of 4.4 × 109 T. Aims. It is the purpose of this paper to study particle acceleration and radiation reaction damping in a rotating magnetic dipole with realistic field strengths of 105 T–1010 T typical of millisecond and young pulsars and of magnetars. Methods. To this end, we implemented an exact analytical particle pusher including radiation reaction in the reduced Landau–Lifshitz approximation where the electromagnetic field is assumed constant in time and uniform in space during one time step integration. The position update is performed using a velocity Verlet method. We extensively tested our algorithm against time independent background electromagnetic fields like the electric drift in cross electric and magnetic fields and the magnetic drift and mirror motion in a dipole. Finally, we apply it to realistic neutron star environments. Results. We investigated particle acceleration and the impact of radiation reaction for electrons, protons, and iron nuclei inserted around millisecond pulsars, young pulsars, and magnetars, in comparison to situations without radiation reaction. We found that the maximum Lorentz factor depends on the particle species, but only weakly on the neutron star type. Electrons reach energies up to γe ≈ 108 − 109, whereas protons reach energies up to γp ≈ 105 − 106 and iron up to γ ≈ 104 − 105. While protons and iron are not affected by radiation reaction, electrons are drastically decelerated, reducing their maximum Lorentz factor by four orders of magnitude. We also found that the radiation reaction limit trajectories agree quite well with the reduced Landau–Lifshitz approximation in almost all cases.

Angular trapping of a linear-cavity mirror with an optical torsional spring

Optomechanical systems have attracted intensive attention in various physical experiments. With an optomechanical system, the displacement of or the force acting on a mechanical oscillator can be precisely measured by utilizing optical interferometry. As a mechanical oscillator, a suspended mirror is often used in over a milligram scale optomechanical systems. However, the tiny suspended mirror in a linear cavity can be unstable in its yaw rotational degree of freedom due to optical radiation pressure. This instability curbs the optical power that the cavity can accumulate in it and imposes a limitation on the sensitivity. Here, we show that the optical radiation pressure can be used to trap the rotational motion of the suspended mirror without additional active feedback control when the $g$ factors of the cavity are negative and one mirror is much heavier than the other one. Furthermore, we demonstrate experimentally the validity of the trapping. We measured the rotational stiffness of a suspended tiny mirror with various intracavity power. The result indicates that the radiation pressure of the laser beam inside the cavity actually works as a positive restoring torque. Moreover, we discuss the feasibility of observing quantum radiation pressure fluctuation with our experimental setup as an application of our trapping configuration.

Transparency and Enhancement in Fast and Slow Light in q‐Deformed Optomechanical System

AbstractNonclassical phenomena can be enhanced by introducing q‐deformation in optomechanical systems. This motivates investigation of the optical response in a q‐deformed linearly coupled optomechanical system. The system consists of two deformed cavities that are linearly coupled to the motion of mechanical mirrors, and the cavities are coupled to each other by transmission strength parameter. This study shows that compared to non‐deformed cases, the deformed system exhibits more rapid phase transition at the positions of transparency windows, causing stronger and enhanced fast and slow light phenomena. Moreover, in the region , the optomechanical system results in gain. Additionally, for a fixed deformation of cavities, by tuning the tunneling strength and optomechanical coupling, one can observe a delay and advancement in probe field in the order of milliseconds and even above milliseconds for fine‐tuning of the coupling parameters. Finally, the bridge between mathematical and physical models is built by assuming the deformation to be a primitive root of unity, which indicates a class of anyon models. These results demonstrate that q‐deformation provides a novel method for manipulating and significantly enhancing optical phenomena not only in arbitrarily deformed optomechanical systems but also in anyon models.

A Hybrid Mechanism-Based Robot for End-Traction Lower Limb Rehabilitation: Design, Analysis and Experimental Evaluation

Conventional lower-limb rehabilitation robots cannot provide in-time rehabilitation training for stroke patients in the acute stage due to their large size and mass as well as their complex wearing process. Aiming to solve the problems, first, a novel hybrid end-traction lower-limb rehabilitation robot (HE-LRR) was designed as the lower-limb rehabilitation requirement of patients in the acute stage, in this paper. The usage of (2-UPS + U)&(R + RPS)&(2-RR) hybrid mechanism and a mirror motion actuator had the advantages of compact structure, large working space and short wearing time to the HE-LRR. Then, the mobility of the HE-LRR was calculated and the motion property was analyzed based on screw theory. Meanwhile, the trajectory planning of the HE-LRR was carried out based on MOTOmed® motion training. Finally, the motion capture and surface electromyography (sEMG) signal acquisition experiments in the MOTOmed motion training were performed. The foot trajectory experimental effect and the lower-limb muscle groups activation rules were studied ulteriorly. The experimental results showed that the HE-LRR achieved good kinematic accuracy and lower limb muscle groups training effect, illustrating that the HE-LRR possessed good application prospects for the lower-limb rehabilitation of patients in the acute stage. This research could also provide a theoretical basis for improving the standardization and compliance of lower-limb robot rehabilitation training.

Non-degenerate two-wave mixing in the subwavelength periodic motion regime

We experimentally study non-degenerate two-wave mixing where reflection from a moving mirror is used to create frequency shifts and show that both the subwavelength motion of the mirror and periodic reversal of the intensity grating direction significantly affect the frequency dependence of the two-wave mixing signals detected both in ruby and colloidal media. It is shown that the Doppler shifts are suppressed when the reflecting moving mirror excursions are small compared to a wavelength and that the periodic reversal of the mirror motion results in a response that does not produce the expected maximum at the grating relaxation time. An approximate theoretical model agrees well with the results of the experiments and elucidates the transition from the observed response to the previously described idealized Doppler shift models.

Calculation of the incidence angle modifier of a Linear Fresnel Collector: The proposed declination and zenith angle model compared to the biaxial factored approach

Since their first appearance as a contribution by Professor Francia at the University of Genova, Italy, the Linear Fresnel Collectors (LFC) demonstrated to be an engineering efficient technology for medium to high temperature solar applications. The strength of the LFC concept is related to the simple mirror motion law, to the compactness of the mirror fields (power to land surface ratios), to the lowest resistance to wind, to the system intrinsic scalability. To perform reliable LCOE analyses, robust performance simulation tools are needed. The Authors developed to this aim a 3D ray-tracing model, able to account for shading, blocking, and end effects as a function of LFC geometry, including primary and secondary mirror curvatures. In this paper, a new approach is implemented to reduce huge yearly ray-tracing datasets and provide very compact analytical equations for fast hourly performance simulations. The present model introduces new Incidence Angle Modifier (IAM) correlations based on the declination and zenith angles. The new model demonstrated to fit subhourly 3D ray-tracing data all year long with an overall error lower than 1.5%, well below the best IAM factored models here compared as a general criticism to the biaxial factored approach related to Fresnel applications.

Quantum communication through a partially reflecting accelerating mirror

Motivated by the fact that the null-shell of a collapsing black hole can be described by a perfectly reflecting accelerating mirror, we investigate an extension of this model to mirror semi-transparency and derive a general implicit expression for the corresponding Bogoliubov coefficients. Then, we turn this into an explicit analytical form by focusing on mirrors that are accelerated via an impulsive force. From the so-obtained Bogoliubov coefficients we derive the particle production. Finally, we realize the field coming from left-past spacetime region, passing through the semitransparent moving mirror and ending up to right-future spacetime region as undergoing the action of a Gaussian quantum channel. We study the transmission and noisy generation properties of this channel, relating them to the Bogoliubov coefficients of the mirror's motion, through which we evaluate capacities in transmitting classical and quantum information.

Design of Four-DoF Compliant Parallel Manipulators Considering Maximum Kinematic Decoupling for Fast Steering Mirrors

Laser beams can fluctuate in four directions, which requires active compensation by a fast steering mirror (FSM) motion system. This paper deals with the design of four-degrees-of-freedom (DoF) compliant parallel manipulators, for responding to the requirements of the FSM. In order to simplify high-precision control in parallel manipulators, maximum kinematic decoupling is always desired. A constraint map method is used to propose the four required DoF with the consideration of maximum kinematic decoupling. A specific compliant mechanism is presented based on the constraint map, and its kinematics is estimated analytically. Finite element analysis demonstrates the desired qualitative motion and provides some initial quantitative analysis. A normalization-based compliance matrix is finally derived to verify and demonstrate the mobility of the system clearly. In a case study, the results of normalization-based compliance matrix modelling show that the diagonal entries corresponding to the four DoF directions are about 10 times larger than those corresponding to the two-constraint directions, validating the desired mobility.

Investigation of crackling noise in the vibration isolation systems of the KAGRA gravitational wave detector

Gravitational wave detectors, such as KAGRA, require complex mirror suspension systems to reach high sensitivity. One particular concern in these suspensions is the presence of crackling noise, where motion of the steel crystal structure disturbs material defects, causing impulse force release and exciting mirror motion. Crackling in the Geometric Anti Spring filters (GAS) in KAGRA's suspension system could introduce noise in the gravitational wave detection band. We investigate crackling noise in a miniature GAS with a low-frequency cyclical stress. We developed a scaling law between miniature and KAGRA GAS. Applying experimental results to the scaling law allows us to estimate the upper limit of crackling noise in KAGRA. It is found that crackling noise should be below the target sensitivity for gravitational waves above 60 Hz.

Synchronization motion accuracy measurement method for coordinated five-axis machine tools

The coordinated five-axis machine tools have been used to machine aerospace large thin-walled parts. Synchronization motion accuracy is important during mirror motion process. This paper develops a method for detecting the synchronous motion accuracy of this kind of system. By measuring the trajectory errors of two tool center positions corresponding to different tool lengths on both sides, the synchronization motion tool center point error and tool axis direction error can be calculated. Simulation and experiments are conducted to verify its effectiveness.

Mirror motion recognition method about upper limb rehabilitation robot based on sEMG

A novel method of mirror motion recognition by rehabilitation robot with multi-channels sEMG signals is proposed, aiming to help the stroked patients to complete rehabilitation training movement. Firstly the bilateral mirror training is used and the model of muscle synergy with basic sEMG signals is established. Secondly, the constrained L1/2-NMF is used to extracted the main sEMG signals information which can also reduce the limb movement characteristics. Finally the relationship between sEMG signal characteristics and upper limb movement is described by TSSVD-ELM and it is applied to improve the model stability. The validity and feasibility of the proposed strategy are verified by the experiments in this paper, and the rehabilitation robot can move with the mirror upper limb. By comparing the method proposed in this paper with PCA and full-action feature extraction, it is confirmed that convergence speed is faster; the feature extraction accuracy is higher which can be used in rehabilitation robot systems.

Principle of the moving-wedge-pair interferometer and modeling of surface non-flatness of the wedge

In this work we propose a new moving optical wedge interferometer for Fourier transform spectroscopy. This is based first on using two couples of wedges, one wedge arm in each arm. For each couple of wedges there is a mirror attached to one wedge. Second, we move one wedge of each couple. The moving wedges in both arms are fixed to each other so they both move rigidly. This increased the factor multiplied by the wedges motion to obtain optical path difference (OPD) twice. This factor showed dependence on the wedge refractive index and wedge angle. First, this factor is less than two which suppresses motion error effects of the wedge. This is compared to motion of mirror in ordinary Michelson interferometer (MI) where the factor is two. Then this factor increases more than two and less than four. This suppresses motion error effects when compared to pair motion error with factor of four. Also, the increase of this factor increases the span of OPD thus improves resolution. Further, the wedge interferometer was proposed to suppress motion errors when compared ordinary MI but it may produce errors when the surface of the wedge is not flat. So, we discuss the problem of surface non-flatness of the wedge. We used the visibility to model the deterioration of the interferogram due to surface non-flatness.

A magnetic velocity Verlet method

We discuss an extension of the velocity Verlet method that accurately approximates the kinetic-energy-conserving charged particle motion that comes from magnetic forcing. For a uniform magnetic field, the method is shown to conserve both particle kinetic energy and magnetic dipole moment better than midpoint Runge–Kutta. We then use the magnetic velocity Verlet method to generate trapped particle trajectories, both in a cylindrical magnetic mirror machine setup and for dipolar fields like the earth's magnetic field. Finally, the method is used to compute an example of (single) mirror motion in the presence of a magnetic monopole field, where the trajectory can be described in closed form.