Mirror Optical System Research Articles

Development of a Compact NDIR CO2 Gas Sensor for a Portable Gas Analyzer

A carbon dioxide (CO2) gas sensor based on non-dispersive infrared (NDIR) technology has been developed and is suitable for use in portable devices for high-precision CO2 detection. The NDIR gas sensor comprises a MEMS infrared emitter, a MEMS thermopile detector with an integrated optical filter, and a compact gas cell with high optical coupling efficiency. A dual-ellipsoid mirror optical system was designed, and based on optical simulation analysis, the structure of the dual-ellipsoid reflective gas chamber was designed and optimized, achieving a coupling efficiency of up to 54%. Optical and thermal simulations were conducted to design the sensor structure, considering thermal management and light analysis. By optimizing the gas cell structure and conditioning circuit, we effectively reduced the sensor’s baseline noise, enhancing the overall reliability and stability of the system. The sensor’s dimensions were 20 mm × 10 mm × 4 mm (L × W × H), only 15% of the size of traditional NDIR gas sensors with equivalent detection resolution. The developed sensor offers high sensitivity and low noise, with a sensitivity of 15 μV/ppm, a detection limit of 90 ppm, and a resolution of 30 ppm. The total power consumption of the whole sensor system is 6.5 mW, with a maximum power consumption of only 90 mW.

A high-precision and efficient adaptive alignment method for Cassegrain dual mirror optical system based on machine learning algorithms

The Cassegrain telescope is widely used in aerospace exploration equipment, characterized by compact structure, complex optical path, and high imaging quality. However, due to the difficulty in establishing an accurate correspondence between the relative pose and imaging quality of a multi mirror group with real machining errors, the current Cassegrain telescope assembly process is very difficult, with blind operation, time-consuming, and low accuracy. This article proposes a high-precision adaptive alignment method for Cassegrain dual mirror optical systems based on machine learning algorisms, and an experimental adaptive alignment system with uncoupled degrees of freedom is developed. Firstly, the overall architecture of the adaptive alignment method is proposed consists of detection, calculation and alignment modules. In the detection module, the Zernike polynomial coefficient of wavefront aberration of the optical system is detected online through the interferometer, meanwhile the pose coordinates of the secondary mirror is accurately fed back through a 6-DOF nanoscale micro mechanism. In the calculation module, machine learning algorithm is applied to build a nonlinear mapping model between the Zernike coefficient and the pose coordinates of the secondary mirror. In the alignment module, the pose coordinates of the secondary mirror can be forced to adjust to the target position. Then, during the real alignment process, the Zernike coefficient test data of the optical system alignment process is monitored in real time, and the nonlinear mapping model is employed to calculate the pose coordinates and then the misalignment of the secondary mirror. Finally, the alignment module is driven to execute the pose correction according to the calculated misalignment value, realizing a high-precision adjustment of the Cassegrain dual mirror optical system. Experimental results shows that the average alignment time cost can be dramatically reduced from around 7 days using the current manual alignment method to just 30 minutes using the proposed adaptive alignment method for achieving a current standard alignment accuracy of wavefront aberration root mean square (RMS) less than 0.1λ, which greatly improves the assembly efficiency. This study proposes a new method for high-precision and efficient alignment of optical systems based on artificial intelligence and contributes to the efficiency improvement for optical assembly.

Issues of laser welding technology of the ends of heat exchange pipes in pipe gratings.

The paper shows that the reliability and service life of shipboard heat exchangers largely depends on the quality of fixing heat exchange pipes in pipe grids. The methods of fixing pipes in a pipe grid depends on many factors: the type of heat exchanger, the material from which the pipes and pipe grids are made, the thickness of pipes and pipe grids, technological capabilities taking into account the chosen design, etc. One of the most effective ways of fixing pipes in the tube grids of heat exchangers is welding. Welds are characterized by strength, manufacturability, and provide a high service life of the joint.
 In the article, it is proposed to use laser welding to perform welded joints. Laser welding provides a high focused energy density concentrated on a very small area with relatively low energy input and heating of adjacent metal layers. In laser welding, there is no strong ionizing radiation, the magnetization of the workpieces does not affect the laser beam, which is relevant when welding magnetic materials. The effect of laser radiation is highly local, carried out in the air, including in the environment of protective gases. Thanks to this, laser welding can be used without problems to connect large-sized metal structures.
 The laser beam is easily transported with the help of mirror optical systems or through a light guide and is directed to hard-to-reach places. At the same time, reliable and operational control of the laser welding process with adjustable energy characteristics is provided. The article describes the technological equipment that can be used for welding heat exchange pipes and pipe gratings.

Моделі аберацій гіперболічних відбивачів другого і вищого порядку кривизни в системах передачі променевої енергії

The processes of ray energy transfer using hyperbolic formations and the accompanying effects are considered. A new concept of the optical system of a solar energy concentrator and varieties within its framework are proposed, aberrations that occur in such systems and the possibility of transmitting ray energy using a hyperboloid system consisting of surfaces of the second and higher order are considered. The possibility of creating the effect of self-focusing in mirror optical systems is considered.

Laboratory demonstration of the prediction of wind-blown turbulence by adaptive optics at 8 kHz with use of LQG control.

The low-latency adaptive optical mirror system (LLAMAS) is designed to push the limits on achievable latencies and frame rates. It has 21 subapertures across its pupil. A reformulated version of the linear quadratic Gaussian (LQG) method predictive Fourier control is implemented in LLAMAS; for all modes, it takes just 30µs to compute. In the testbed, a turbulator mixes hot and ambient air to produce wind-blown turbulence. Wind prediction clearly improves correction when compared to an integral controller. Closed-loop telemetry shows that wind-predictive LQG removes the characteristic "butterfly" and reduces temporal error power by up to a factor of three for mid-spatial frequency modes. Strehl changes seen in focal plane images are consistent with telemetry and the system error budget.

Measurement of Gloss Unevenness with Different Reflection Angles

In this study, we introduced a measurement method for gloss unevenness as a function of reflectance angles. Gloss is one of the most important qualities of materials, and it is evaluated subjectively by the intensity of reflected light and gloss unevenness. People can estimate the texture of a material using gloss unevenness, which is found in the small peripheral part of the gloss area and can easily be recognized by observing the reflected light while moving the object or eyes. However, it is not easy to photograph and quantify gloss unevenness. One reason is the area where gloss unevenness is observed is a small area near specular reflection. Second, the appearance of gloss unevenness changes depending on the reflection angle. We developed a measurement apparatus to measure gonio-photometric gloss unevenness. We introduced two solutions: a wide-area gloss unevenness measurement technology using telecentric imaging and a rotating mirror optical system that defects reflected light at an angular resolution of 0.02°. We analyzed three materials—mirror, plastic, and paper—and proposed three indicators as a quantitative evaluation method for gloss: intensity of reflected light at the specular angle, full width at half maximum (FWHM) of Bidirectional Reflectance Distribution Function (BRDF), and gloss unevenness image at the FWHM.

Programming polymorphable yet stiff truss metamaterials in response to temperature

Shape morphing in response to an external stimulus can create geometric transformations from initially flat materials. Current strategies rely on thin layers made of soft materials that are inherently floppy to provide morphability, but cannot support their own weight and must forgo structural resistance, hence limiting their use as structural materials. Here, we demonstrate thermally actuated shape morphing of a three-dimensional framework that can evolve into complex, lightweight shapes that are both stiff and morphable, hence resolving the conflict between rigidity and morphability. Our building block is a truss unit cell that leverages the mismatched thermal expansions of its rigid constituents to generate programmable spatial deformation. By encoding specific geometric and multimaterial attributes into the truss system, we realize shape morphing on target and generate reversible structural transformations with complex curvature combinations. We also explore cooling and localized heating, unveiling temperature-dependent morphological evolutions and heat-source tracking. The morphable, yet stiff, truss metamaterial here introduced has potential applications in thermally responsive smart buildings, thermal management adaptive devices, deployable shelters in extreme environments, and mirror optical systems in space.

Active vibration control of a polyvinylidene fluoride laminated membrane plate mirror

Lightweight optical mirrors usually play key roles in aerospace and optical structural systems applied to space telescopes, radars, solar collectors, communication antennas, etc. Due to their high flexibility and low damping properties, external excitations such as orbital maneuver may induce unexpected oscillations and thus reduce their working performance. Active vibration control is therefore essential for the lightweight optical mirror systems. In this spirit, a lightweight mirror structronic system with a linear quadratic optimal controller is presented. The mirror is modeled as a membrane plate with pretension and distributed polyvinylidene fluoride sensors and actuators. The sensing sensitivity of the piezoelectric (PVDF) sensors and the modal actuation factor of the PVDF actuators are derived. The state-space equations are established and the feedback control gains between sensing and control signals are obtained. Sensor and actuator of different shape, size, and position are employed to actively control the first four natural modes of the mirror. The influences of mode order, pretension, and the two weighting factors Q and R on the control performance are also investigated. Analytical results in this paper could guide the design and layout of the PZT sensor and actuator on lightweight membrane plate mirrors.

Research on Key Technologies of MEMS-based 3D Imaging LIDAR Vision System

In this paper, a new type of 3D imaging light detection and ranging (LIDAR) vision system based on Micro-Electro-Mechanical System (MEMS) mirror and novel optical system is proposed. The co-aperture transceiver optical system offers a compact architecture and wide Field-of-View (FOV), which also solves the problem of stray light affecting the system. Thanks to the MEMS and the optical system, the detecting FOV is greatly enlarged and the system volume is much smaller compared to the traditional system. The whole system is designed and verified by simulations and experiments.

Surface Correction Control Based on Plasticized Multilayer P(VDF‐TrFE‐CFE) Actuator—Live Mirror

AbstractThe interdisciplinary approach presented here creates next‐generation large mirrors using electroactive polymer (EAP) actuators without classical glass abrasive polishing (“live mirrors”). The outstanding electromechanical coupling properties of terpolymer are taken advantage of, particularly when doped with plasticizer, e.g., diisononyl phthalate (DINP). This doped terpolymer creates a large strain response as well as excellent mechanical energy density under relatively low electric fields. Classical EAPs (e.g., polyurethane, silicone) require extremely high input voltages to reach sufficient mechanical strain. Using the high‐permittivity doped terpolymer and the concept of stacking multilayers, high displacements and large forces are generated. The actuation performance of multilayered terpolymer filled with DINP has been proven to shape mirror glass with a preliminary prototype of an 8‐layer actuator stack. The experimental results demonstrate surface deformations under load conditions of several microns. This is large enough to usefully control large optical telescope mirrors. This technology may enable much larger high‐quality optical mirror systems for ground‐ and space‐based astronomy and communications telescopes.

The Effectiveness Analysis Due to the Use of Lagrange Equation and the Optimization Technology for Design of the Support Structure of the Optical Mirror System

The Effectiveness Analysis Due to the Use of Lagrange Equation and the Optimization Technology for Design of the Support Structure of the Optical Mirror System

Design and tolerance analysis of infrared offaxis threemirror optical system with large aperture

Design and tolerance analysis of infrared offaxis threemirror optical system with large aperture

镜面散射对离轴三反系统成像质量的影响

镜面散射对离轴三反系统成像质量的影响

Thermally stable amorphous tantalum yttrium oxide with low IR absorption for magnetophotonic devices

Thin film oxide materials often require thermal treatment at high temperature during their preparation, which can limit them from being integrated in a range of microelectronic or optical devices and applications. For instance, it has been a challenge to retain the optical properties of Bragg mirrors in optical systems at temperatures above 700 °C because of changes in the crystalline structure of the high–refractive-index component. In this study, a ~100 nm–thick amorphous film of tantalum oxide and yttrium oxide with an yttrium-to-tantalum atomic fraction of 14% was prepared by magnetron sputtering. The film demonstrated high resistance to annealing above 850 °C without degradation of its optical properties. The electronic and crystalline structures, stoichiometry, optical properties, and integration with magnetooptical materials are discussed. The film was incorporated into Bragg mirrors used with iron garnet microcavities, and it contributed to an order-of-magnitude enhancement of the magnetooptical figure of merit at near-infrared wavelengths.

Enhanced Disturbance Observer Based on Acceleration Measurement for Fast Steering Mirror Systems

In this paper, a modified disturbance observer (DOB) for fast steering mirror (FSM) optical system based on a charge-coupled device (CCD) and inertial sensors is proposed. Combining a DOB with the classical cascaded multiloop feedback control, including position loop, velocity loop, and acceleration loop, that the disturbance suppression performance of line-of-sight in an FSM system can be significant improved. However, due to the quadratic differential in the FSM acceleration open-loop response, in fact, it is very difficult to realize an integral algorithm to compensate a quadratic differential in practical application. Thus, the conventional DOB controller has to be simplified further to make a concession, which eventuates in still insufficient disturbance compensation, particularly at low frequency. To solve this problem, an enhanced DOB control structure, which changes the compensation plant to be the acceleration open-loop and avoids the saturation of double integration skillfully, is proposed. The recommended method optimizes the controller design, which is conducive to controller fulfillment in practical systems. A series of comparative experimental results demonstrate that the disturbance suppression performance of the FSM control system can be effectively improved by the proposed approach.

Research on segmented mirror position error of optical system based on ZEMAX

We have modeled a segmented mirror optical system by software ZEMAX, and analyzed influence of segmented mirror’s position error to the optical system imaging for the first time to author’s best knowledge. The primary mirror is composed of 18 segmented mirrors. By adjusting each one’s position error of six freedoms, we get six relationship curves between position error and the optical system’s image quality. The relationship curves show that some have different wave-front error RMS values when segmented mirrors have same position errors. The middle mirrors are sensitive to the movement along X axis direction, and the outer ones are sensitive to the movement along Y axis direction. The middle ones and outer ones are all sensitive to the tilt error, especially tilt along X, Y axis.

Physical optics analysis of a three-dimensional radiating structure

We discuss radiating structures in an infrared mirror optical system exposed to external thermal and mechanical effects and affected by significant deformations that affect the directional patterns of such sources. Deformations distort the radiant surfaces into a complex 3D shape that turns out to be difficult to describe in closed form. We have developed a discrete mathematical model for the radiant structure; this model can be used to study the structural impact of external effects on the infrared source and on the radiation characteristics of the source. Matrix analysis and analytical geometry enabled us to determine the spatial orientation of elementary areas of the deformed radiating surface and to then use physical optics to determine the contribution of each elementary area to the radiation emitted, taking into account the vector nature of the electromagnetic field.

Design of the mirror optical systems for coherent diffractive imaging at the SPB/SFX instrument of the European XFEL

The high degree of spatial coherence and extreme pulse energies available at x-ray free electron laser (XFEL) sources naturally support coherent diffractive imaging applications. In order to optimally exploit these unique properties, the optical systems at XFELs must be highly transmissive, focus to appropriate sizes matched to the scale of samples to be investigated and must minimally perturb the wavefront of the XFEL beam. We present the design and simulated performance of two state-of-the-art Kirkpatrik–Baez mirror systems that form the primary foci of the single particles, clusters and biomolecules and serial femtosecond crystallography (SPB/SFX) instrument of the European XFEL. The two systems, presently under construction, will produce 1 μm and 100 nm scale foci across a 3–16 keV photon energy range. Targeted applications include coherent imaging of weakly scattering, often biological, specimens.

Prevention of image tilt in plane mirror optical systems

Prevention of image tilt in plane mirror optical systems

拼接主镜光学系统展开误差的分析

拼接主镜光学系统展开误差的分析