Mirror Angle Research Articles

High-precision optical modeling method for galvanometer-driven dual-camera systems.

To build a galvanometer-driven dual-camera sensing system, it is important to accurately correlate the wide-view image coordinates with the pan-tilt mirror angles for adjusting the incident light path of the zoom-in camera. Existing optical modeling methods assume sufficient target distance and simplify dual-camera optical centers as coincident. However, this simplification is not valid in many practical cases and might cause severe system malfunctions, such as complete loss tracking of important targets. To address this problem, we propose a novel approach, to the best of our knowledge, to facilitate high-precision optical modeling and calibration of galvanometer-driven dual-camera systems. The proposed method takes into consideration the dual-camera optical center misalignment issue and builds a model for accurate estimation and rectification of target localization errors under various optical configurations. Qualitative and quantitative experimental results demonstrate the superiority of our method, improving the performance of galvanometer-driven dual-camera systems for high-precision optical sensing applications.

A three-dimensional trajectory measurement system for quasi-one-dimensional high-speed moving objects

Abstract The three-dimensional (3D) trajectory measurement of a quasi–one-dimensional (quasi-1D) high-speed moving object often cannot achieve the optimizations of both the measurement range and the object’s resolution at the same time. In this paper, a 3D trajectory measurement system for quasi-1D high-speed moving objects is proposed. The system was composed of a single camera and a galvo mirror. The posture of the virtual camera is changed by adjusting the angle of the galvo mirror, thereby achieving the tracking and imaging of a quasi-1D high-speed moving object. For a background with complex textures, a measurement method based on the reconstructed homography matrix is proposed. The extrinsic matrix of the virtual camera is estimated based on the feature points on the background, and the equation of the object trajectory’s plane is estimated based on the feature points on the object. Then, by combining the extrinsic matrix and the equation of the plane, a new homography matrix is reconstructed, realizing the measurement of the 3D coordinates of the object. For a background with weak textures, a method based on the deflection angle of the galvo mirror is proposed for the calibration of the extrinsic matrix of the virtual camera. This method can calculate the extrinsic matrix of the virtual camera based on the distance from the camera to the center point of the galvo mirror and the deflection angle of the galvo mirror. The experimental results show that the proposed system is able to increase the field of view by 430%. For complex-texture backgrounds, the relative error of the system is 0.79%, and for weak-texture backgrounds, the relative error is 4.65%.

Single detector compound axis system employs a two-axis mirror to achieve target acquisition

Airborne electro-optical countermeasure systems necessitate designs that are both lightweight and miniaturized. This study examines a single-detector composite-axis system that integrates a large-stroke, large-aperture two-axis mirror for coarse tracking tasks and a piezoelectric fast-steering mirror for fine tracking adjustments. Addressing the system’s initial pointing and spiral scanning challenges, the study derives dynamic target-pointing equations using coordinate transformation and optical geometry. Neural network fitting is utilized to analyze the coupling between the mechanical travel angle of the two-axis mirror and the optical angle changes. Scanning detection and image motion compensation techniques enhance the system’s field of view. The paper also introduces the application of differential evolution algorithms for target positioning without distance information. Ground-to-air experiments substantiate the effectiveness of the proposed methods.

Influence of geometric design variables on the performance of a novel V-shaped cavity receiver

This study presents a novel cavity receiver for parabolic trough concentrators, incorporating a triangular envelope, a trapezoidal cavity, and a semi-circular flow channel. A total of 5120 designs were examined by tuning the rim angle of parabolic mirrors, the width and angle of the receiver's opening, and the depth of the absorber for different operating flow rates and temperatures. Batch simulations of these designs were automated by coupling newly developed and validated models of Monte Carlo ray tracing and semi-analytical 1-D energy balances in SOLTRACE® and MATLAB® to determine the heat fluxes and surface temperatures of the receiver, respectively. The results show that the rim angle must be reduced to maximize sun rays' interception, and the opening angle has the largest impact on performance. All dimensions must be decreased when operating at low flow rates and high temperatures to avoid excessive thermal losses. This results in maximum energy and exergy efficiencies of 74.7 % and 40.7 %, respectively. When operating at low temperatures and large flow rates, the largest energy and exergy efficiencies increase and decrease to 80.5 % and 27 %, corresponding to optimal rim angle, absorber depth, opening width, and opening angle of 60°, 85 mm, 200 mm, and 100°, respectively.

Design of a Fourier-transform spectrometer for detector characterization on CMB polarization telescope

We present the design of a Fourier-transform spectrometer (FTS) tailored for operation within the frequency range of 75 GHz to 300 GHz, offering a spectral resolution surpassing 2 GHz. This FTS can be used for characterizing detectors on a Cosmic Microwave Background (CMB) Polarization Telescope for the observation of CMB B-mode polarization. The FTS instrument is divided into the primary part, housing a Martin-Puplett interferometer (MPI) module, and the coupled part, which incorporates a beam expanding module and a beam steering module. An in-depth performance analysis focusing on the MPI module, involving considerations such as the orientation of the beam splitter, dihedral angle of the roof-top mirrors, and positioning uncertainty of the scanning mirror, has been conducted by using a simulation tool. Results indicate that the spectral characteristic remains unaffected by variations in the Reflection/Transmission ratio of the beam splitter, with any deviation from the 1:1 ratio uniformly decreasing intensity. The impact of dihedral angle errors of roof-top mirrors (below 0.02 degrees) and positioning uncertainty in the scanning mirror (lower than 3 × 10-3 mm) on the system performance is acceptable for the design of the FTS. The beam expanding module is capable of enlarging the output beam of the MPI module to roughly a 150 mm-radius. The beam steering module allows for directional adjustments within the range of +17 degrees to -17 degrees relative to the normal of the target plane. Preliminary testing on the MPI prototype reveals a spectral resolution of 1.5 GHz for the measured frequency.

Design of in-vessel mirror of ITER poloidal polarimeter

Diagnostics in-vessel mirrors receive high neutron heating loads and high radiation heat loads because it directly faces the plasma. The in-vessel mirror of this study consists of three layers; tungsten mirror, copper-alloy heatsink and stainless-steel mirror mount. The copper-alloy heatsink is actively cooled by cooling-water pipe. The tungsten mirror is attached to the heatsink with contact pressure of 3.5 MPa and is cooled by thermal conduction to the heatsink. The mirror is not rigidly fixed to the heatsink but is able to slide on the surface of the heatsink because thermal stress in the dissimilar materials during baking needs to be avoided. The structural integrity was evaluated according to RCC-MRx code. The highest primary load to the mirror was the acceleration load during plasma disruption, and the highest secondary load was the baking temperature (240 °C). All design criteria specified in RCC-MRx code are satisfied. In addition, the design of the in-vessel mirrors was developed to facilitate adjustment of mirror angle with accuracy of 0.1° A prototype mirror was made to confirm the surface deformation owing to the assembly load. Surface deformation was 6.3 μm and was sufficiently small compared to the laser wavelength.

Accurately estimating the scanning angle of an electrostatic MEMS mirror with a novel damping model

A novel damping model to accurately analyze the scanning angle of electrostatic microelectromechanical system (MEMS) mirrors is proposed in this article. The computational fluid dynamic (CFD) simulations are used to calculate the aerodynamic moment of the MEMS mirror oscillating in air. The simulation results demonstrate the linear dependence of the equivalent damping coefficient of the MEMS mirror on the oscillation amplitude and frequency. Then the equivalent damping expression of the MEMS mirror is established. The damping model is applied to the dynamic equation of the MEMS mirror for numerical solution. The frequency responses of the electrostatic MEMS mirror under square wave excitation with different voltage amplitudes and duty cycles are obtained. The measurement results provide good accuracy verification for numerical results. This verifies the accuracy of the proposed damping model, which can be used to accurately estimate the scanning angle in the design and parameter optimization process of electrostatic MEMS mirrors.

Controlled generation of OAM-switchable vortex beams at 639 nm from a Pr3+: YLF laser

In this paper, we reported and demonstrated a blue LD-pumped Pr3+: YLF laser for the controlled generation of orbital angular momentum (OAM) switchable vortex beams at 639 nm. To begin with, the quantitative tilt imbalance of the resonator was introduced to select the higher-order Hermite-Gaussian (HG) modes by utilizing the eigenvector method and introducing the concept of mode discriminant factor. Moreover, the mode converter, composed of two cylindrical mirrors, was applied to convert the Hermite- Gaussian (HG) modes into the Laguerre-Gaussian (LG) modes with the OAM. Then, the experiment setup was built to validate the correctness and effectiveness of the quantitative tilt imbalance. The results showed that the vortex beams with OAM of 0 to ±14 at 639 nm can be obtained by adjusting the tilted angle of the output mirror, which agreed well with the simulation results, and the slope efficiencies of the vortex beams with OAM = 1, 2, and 3 are 11.64%, 8.01%, and 6.05%, respectively. The method provided a viable solution for the generation of visible vortex beams with switchable OAM from the Pr3+: YLF laser.

Period-multiplying pulses generation by total self-mode-locking of Nd:YVO4 lasers

We experimentally demonstrated the phenomenon of period-multiplying pulses in the self-mode-locking Nd:YVO4 laser. With a fixed cavity length of 50 mm and the input mirrors in the resonator with radii of curvature of 100 mm, 200 mm, and 500 mm, the mode-locked pulses with pulse periods 4 times, 6 times and 10 times the fundamental mode-locked pulse period are observed respectively. Besides, by tilting the angle of the output mirror to control the spatial distribution of transverse modes, the switching between the period-multiplication state and its harmonic self-locking state can be achieved. Numerical simulations further confirm that this period-multiplying phenomenon results from the simultaneous locking of multi-longitudinal and multi-transverse modes. This study is of great significance for understanding the complex transverse dynamics in the self-mode-locking lasers.

Evaluation and analysis of target interpretation capability for novel rotating synthetic aperture system

The novel rotating synthetic aperture imaging system has the advantages of short processing cycle, light weight, low cost, and convenient transport, which is a potential development direction for future optical satellite payloads with ultra-large aperture. However, influenced by the coupling effects of the rectangular primary mirror, rotating imaging, and link perturbation, images from this system may have unique spatial and temporal variability with resolution anisotropy, resulting in the dynamics and weak features of targets. The insufficient recognition of system characteristics seriously restricts the application ability of corresponding target interpretation methods. To address this problem, we start with the analysis of system imaging characteristics and target interpretation mechanisms. Considering calculating texture, grayscale, and edge feature parameters in evaluation regions of different sizes, we propose a degradation assessment method based on multi-scale feature characterization. Then, combined with the theoretical calculation and practical target detection experiments, the influence of crucial parameters such as the aspect ratio and rotation angle of the primary mirror on the target interpretation capability is analyzed. The results will provide guidance for the integrated design and optimization of optical imaging systems and intelligent image processing methods.

High energy laser & systems to neutralise stellar coronal mass ejections (CME) plasma

With CME plasma and shockwave travelling at 600+ km/sec, active methods such as high energy electron lasers (HEL) and mirrors are effective at making contact with ionised atoms in CME. Electrons pulsed from kW to MW laser(s) could polarise ionised atoms such as Fe16+, O7/8+, Mg, He2+,etc to fill valence pairs. As high-FIP atoms are electromagnetically trapped with a higher susceptibility from lower e- density and temperatures, CME plasma clouds can be neutralised, separated, and reduced in velocity trajectory around planet. Study outlines interactions between Electron Laser and CME plasma cloud, orbital geometry, build of high energy lasers, subsystems, as well as recoils, and cloud charge dynamics with e- interactions to neutralise CME particles. Additional space-based systems are designed such as mirrors in closer orbit to align lower velocity light beams. In approaching higher electron recombination and FIP ionisation of laser-plasma ion cluster density, max absorption of e- to CME could be approached with similar beam, CME, mirror angles and alignment, where e- couple and fill valence shells. Models evaluate efficacy of coherent laser beams of charged electrons, X-rays, infrared (IR), and/or electron/radio Hz to polarize CME column charge densities, with optimal CME scatter geometry and time window. Low cost ground experiments are discussed. Models suggest every ~1 km gap laser creates when CME t=8.255min creates a 10,067 km gap for Earth to orbit through. Such a HEL laser, reflecting mirrors, and space systems could neutralize plasma CME Cloud within 92.818M mi (Sun-Earth distance) and mitigate effects and trillion dollar costs from Carrington-type CME flares, and supernovae.

Methane gas spectral imaging method based on dual wedge scanning mirrors

With the increase in the number of oil and gas pipelines laid in China, more attention needs to be paid to pipeline maintenance work. At present, the main methods of detecting natural gas leaks in oil and gas transmission stations include manual inspections, opposing natural gas detection equipment, and cloud desktop natural gas detection equipment. Hand held natural gas detection equipment is used for manual inspection, which requires regular manual inspection. However, the response speed is poor and gas leaks cannot be detected in a timely manner. The opposed laser gas detection method can only detect the presence of gas on the beam path. If a larger area of leakage detection is desired, more equipment needs to be installed, resulting in a greatly increase in hardware costs. The existing cloud desktop laser gas detection method controls the deflection of the laser beam through the cloud platform to achieve leak detection at various points in the area to be tested. However, the rotation speed of the cloud platform is slow, and a complete detection cycle takes dozens of minutes, and only the presence of gas can be detected. For accurate leak location, manual on-site survey is also required to further determine the leak location. In order to meet the needs of the real-time monitoring and rapid positioning of oil and gas pipeline leaks, in this work, a fast and accurately controlled dual wedge scanning mirror system is designed, which combines tunable semiconductor laser absorption spectroscopy technology to convert the gas measurement laser beam from point measurement to surface measurement, thereby obtaining the two-dimensional distribution of gas, which is conducive to subsequent analysis and positioning of gas leakage sources. By using the inverse solution iterative optimization algorithm, the angle of the wedge mirror is controlled to obtain an efficient and uniform beam scanning trajectory. The deflection direction and detection position of the laser beam are fused with the corresponding methane concentration information, and a methane concentration data containing position information is constructed. In order to quantitatively verify the measurement accuracy and spatial resolution in the experiment, a standard air bag is used to simulate the methane leakage distribution. The results show that the minimum detection limit of the system can be lower than 5×10<sup>–4</sup> m, and the spatial resolution can be less than 6 cm. At the same time, this method can adjust the scanning step node based on the measurement distance of the oil from gas station, thereby achieving adjustable imaging resolution. This imaging method provides a new idea for accurately positioning and detecting the methane leakage location and amount.

A fast calculation method for deflection angles of dual fast steering mirrors for beam pointing control

A fast calculation method for deflection angles of dual fast steering mirrors for beam pointing control

Research on Model and Detection Range of Mirror Angle Detection Based on Quadrant PD and LED

Research on Model and Detection Range of Mirror Angle Detection Based on Quadrant PD and LED

Automatic Adjustable Rear-View Mirror Using Servo Motor and Arduino for Bikes

Abstract: The Automatic Adjustable Rear-View Mirror (AARM) system utilizing a servo motor and Arduino for bikes is an innovative solution aimed at enhancing rider safety and convenience. This is an automotive aid for riders, as many times we see that side glass or rear view mirrors of two wheelers are maximum time disorientated and riders barely takes any precaution against it. This system employs servo-controlled mechanisms to enable automatic adjustment of the rear-view mirror angles based on real-time riding conditions. By integrating an Arduino microcontroller, the AARM system achieves dynamic responsiveness to varying situations, providing riders with optimal visibility without manual intervention.

Effect of external magnetic fields on practical quantum random number generator

Quantum random number generator (QRNG) based on the inherent randomness of fundamental quantum processes can provide provable true random numbers which play an important role in many fields. However, the security of practical QRNGs is linked to the performance of realistic devices. In particular, devices based on the Faraday effect in a QRNG system may be affected by external magnetic fields, which will inevitably open a loophole that an eavesdropper can exploit to steal the information of generated random numbers. In this work, the effects of external magnetic fields on the security of practical QRNGs are analyzed. Taking the quantum phase fluctuation based QRNG with unbalanced Michelson interferometer as an example, we experimentally demonstrate the rotation angle of the Faraday rotation mirror (FRM) is influenced by external magnetic fields. Then, we develop a theoretical model between the rotation angle deviation of FRM and conditional min-entropy. Simulation results show that the imperfect FRM leads to a reduction in the variance of measured signal and extractable randomness. Furthermore, the impacts of practical sampling device on the extractable randomness are analyzed in the presence of imperfect FRM, which indicates suitable parameters of the sampling device can improve the security of practical QRNGs. Potential countermeasures are also proposed. Our work reveals that external magnetic fields should be carefully considered in the application of practical QRNGs.

High-Range and High-Linearity 2D Angle Measurement System for a Fast Steering Mirror.

In order to solve the problem of the insufficient range of the traditional fast mirror (FSM) angle measurement system in practical applications, a 2D large-angle FSM photoelectric angle measurement system based on the principle of diffuse reflection is proposed. A mathematical model of the angle measurement system is established by combining the physical properties of the diffuse reflecting plate, such as the rotation angle, rotation center, rotation radius, reflection coefficient and the radius of the diffuse reflecting surface. This paper proposes a method that optimizes the degree of nonlinearity based on this mathematical model. The system is designed and tested. The experimental results show that changing the diffuse reflection surface area can improve the nonlinearity of the angle measurement system effectively. When the radius of the diffuse reflection surface is 3.3 mm, the range is ±20°, the non-linearity is 0.74%, and the resolution can reach up to 2.3″. The system's body is simple and compact. It is also capable of measuring a wider range of angles while linearity is guaranteed.

Experimental study of a linear Fresnel reflection solar concentrating system

Introduction: In the field of solar energy utilization, the construction of low cost and easy to process large concentrated photothermal system is a scientific problem to be solved. A linear Fresnel reflection solar concentrator is proposed in this paper.Methods: The position, tilt angle and width of the glass mirrors placed in the same plane are different to ensure that all the reflected light falls on the flat focal plane or cylindrical focal surface. According to the focusing principle of the concentrator, two experimental system platforms ware built. When a flat focal plane is used to receive radiation from the sun, the intensity distribution of focal plane light spot is uniform in theory.Results: The CCD measurement method is used to analyze the concentrated light spot under experimental conditions, and it is proved that the energy flux density on the focal plane is uniform. Placing monocrystalline silicon cells on the focal plane, the experimental results of p-v power generation voltammetry show that the power generation efficiency of monocrystalline silicon cell does not decrease due to the uniform solar energy density, which can reach 17.1%. The photothermal experiment is carried out by using one-dimensional tracking mode of sunlight. The concentrator reflects the sun’s rays onto the vacuum collector tubes, heating the heat conduction oil flow in. The thermocouple measures the temperature of the heat conduction oil at the inlet and outlet of the vacuum collector tubes. The experimental photothermal conversion efficiency of this concentrator was analyzed and calculated through multiple groups of photothermal experiments, and compared with the theoretical concentrator efficiency. With two collector tubes in series, the theoretical photothermal conversion efficiency reaches 0.8 and the experimental photothermal conversion efficiency reaches about 0.74.Discussion: Because of its good concentrating performance and low cost, this type concentrator can be widely used in photothermal and photovoltaic applications.

Comparative assessment of two different designs of box solar cookers under algerian sahara conditions

This paper deals with the experimental study of two box-type solar cookers equipped with booster mirrors and suitable for cooking a single family’s food. The first one has a conventional, ordinary horizontal aperture area and the second one has an inclined aperture area. The latter is a new configuration which allows for much higher solar radiation interception, resulting in better cooking performance, especially in the winter when the sun’s elevation is low. Optimum inclination angles of the booster mirrors were calculated in order to maximize the reflection of the solar rays on the absorber plates. The cooking performance of the proposed new cooker was compared with the conventional box solar cooker of the same material and surface during Winter 2013 in the Ghardaîa Sahara climate (32.39°N, 3.78°E), Algeria. According to the values of some essential thermal performance parameters suggested by International Standards and evaluated by experimental studies, the inclined aperture area improves the thermal performance of the box-type solar cooker remarkably, reducing cooking time considerably. The first and second figures of merit for the improved cooker, respectively, were 0.15 and 0.47 compared to 0.13 and 0.38 for the conventional cooker.

Research on the Performance of Superhydrophobic Cement-Based Materials Based on Composite Hydrophobic Agents.

The utilization of a novel monolithic superhydrophobic cement material effectively prevents water infiltration and enhances the longevity of the material. A method for improving superhydrophobic concrete was investigated with the aim of increasing its strength and reducing its cost by compounding superhydrophobic substances with water repellents. The experimental tests encompassed the assessment of the compressive strength, contact angle, and water absorption of the superhydrophobic cementitious materials. The findings demonstrate that an increase in the dosage of isobutyltriethoxysilane (IBTES) progressively enhances the contact angle of the specimen, but significantly diminishes its compressive strength. The contact angle of SIKS mirrors that of SIS3, with a superior compressive strength that is 68% higher. Moreover, superhydrophobicity directly influences the water absorption of cementitious materials, with a more pronounced superhydrophobic effect leading to a lower water absorption rate. The water absorption of cementitious materials is influenced by the combined effect of porosity and superhydrophobicity. Furthermore, FT-IR tests unveil functional mappings, such as -CH3 which can reduce the surface energy of materials, signifying successful modification with hydrophobic substances.