Optical Mirror Research Articles

Multi-frame blind deconvolution using X-ray microscope images of an in-plane rotating sample

We propose a multi-frame blind deconvolution method using an in-plane rotating sample optimized for X-ray microscopy, where the application of existing deconvolution methods is technically difficult. Untrained neural networks are employed as the reconstruction algorithm to enable robust reconstruction against stage motion errors caused by the in-plane rotation of samples. From demonstration experiments using full-field X-ray microscopy with advanced Kirkpatrick–Baez mirror optics at SPring-8, a spatial resolution of 34 nm (half period) was successfully achieved by removing the wavefront aberration and improving the apparent numerical aperture. This method can contribute to the cost-effective improvement of X-ray microscopes with imperfect lenses as well as the reconstruction of the phase information of samples and lenses.

Semiconductor Laser Packaging Technology: Thermal Management, Optical Performance Enhancement and Reliability Studies

This review article presents a comprehensive and in-depth discussion of thermal management, optical performance enhancement, and reliability issues in semiconductor laser packaging technology. By synthesising existing literature and research results, the article presents a systematic summary of the research progress and practical applications of semiconductor laser packaging technology in these key areas. In the section on thermal management, the article reviews different heat sink technologies, packaging structures, and solid crystal materials with the aim of improving the thermal stability and long-term reliability of semiconductor la ser devices. In the section on optical performance enhancement, the article outlines beam shaping techniques and packaging technologies. It also addresses reliability issues in packaging, discussing optical mirror damage as well as stress and mechanical damage. The aim of this review is to provide assistance for the further development and application of semiconductor laser packaging technology, with the objective of promoting the rapid and healthy development of the laser industry.

Dynamic Characteristics, Analysis, and Measurement of a Large Optical Mirror Processing System

Dynamic Characteristics, Analysis, and Measurement of a Large Optical Mirror Processing System

An indirect geometry crystal time-of-flight spectrometer for FRM II

We present a concept for an indirect geometry crystal time-of-flight spectrometer, which we propose for a source similar to the FRM-II reactor in Garching. Recently, crystal analyzer spectrometers at modern spallation sources have been proposed and are under construction. The secondary spectrometers of these instruments are evolutions of the flat cone multi-analyzer for three-axis spectrometers (TAS). The instruments will provide exceptional reciprocal space coverage and intensity to map out the excitation landscape in novel materials. We will discuss the benefits of combining a time-of-flight primary spectrometer with a large crystal analyzer spectrometer at a continuous neutron source. The dynamical range can be very flexibly matched to the requirements of the experiment without sacrificing the neutron intensity. At the same time, the chopper system allows a quasi-continuous variation of the initial energy resolution. The neutron delivery system of the proposed instrument is based on the novel nested mirror optics, which images neutrons from the position of the pulse cutting chopper representing a bright virtual source onto the sample. The spot size of less than 1 cm × 1 cm at the virtual source allows the realization of very short neutron pulses by the choppers, while the small and well-defined spot size at the sample position provides an excellent energy resolution of the secondary spectrometer.

System Integration Design of High-Performance Piezo-Actuated Fast-Steering Mirror for Laser Beam Steering System.

This paper presents an innovative piezo-actuated fast-steering mirror (FSM) that integrates control design and system operation to improve the tracking performance of laser beam steering (LBS) systems. The proposed piezoelectric FSM is centered on two pairs of stacked actuators functioning in the tip-tilt direction via novel flexible hinges with strain-gauge sensors for position measurement. The suggested flexible hinge scheme allows the first fundamental resonance mode with the optical mirror to exceed 400 Hz while achieving an actuation range of ±5 mrad. Thus, the design offers a wider mechanical actuation range than conventional piezoelectric FSMs. Moreover, LBS systems that use fast-steering motion controllers should be robust against dynamic disturbances, such as periodic external vibrations. Such disturbances, inherently associated with the operating conditions for LBS systems, typically reduce the stability of the tip-tilt motion. To attenuate the effects of such disturbances, a high-precision control system is necessary for the tip-tilt motion. Therefore, a control method integrating a proportional-integral controller with an adaptive feedforward control (AFC) algorithm is outlined to enhance tip-tilt tracking performance during high-speed scanning, compared with conventional LBS systems. Based on experimental findings, the AFC algorithm boosted control performance under dynamic disturbances, such as sinusoidal vibrations with multiple frequencies.

Mid-spatial frequency reduction via zero-depth of cut rapid-feed passes in face-turning

The single point diamond turning process (SPDT) is used widely in creating optical grade mirror surfaces on several engineering materials ranging from polymers, and metals, to brittle materials such as silicon and germanium. In visual optic mirror applications, mid-spatial frequency (MSF) errors generated during the SPDT process interfere with the visible spectrum of light thereby affecting the image quality. To overcome these errors, a post-processing operation of polishing the optical mirrors is required. The post-processing step not only increases the complexity of the manufacturing process but also leads to minor geometrical form changes in the mirror which affects performance. To avoid post-processing and minimize MSFs formed during turning- a novel method to modify the toolpath during the machining process has been proposed in this paper. The suggested toolpath strategy comprises two consecutive operations: i) employing variable low feed rates with the specified depth of cut (DoC) and ii) executing rapid traverse rates with zero depth of cut for a predetermined number of passes. The effectiveness of the proposed strategy is tested by carrying out facing experiments in a micro-precision CNC lathe. The power spectral density (PSD) content of the machined surface is then analyzed to check for any improvement in the frequency characteristics. The results show that the frequency errors generated by the toolpath in normal turning operations can be minimized, distributing the resulting PSD peak over a wide range of spatial frequencies. From the PSD plots, it is observed that there is a decrease of 77% and 85.82% in the peak intensity values when compared with surfaces machined at constant feedrates of 150 μm/rev and 200 μm/rev respectively. This method can be applied to nanoprecision SPDT machines to improve the surface quality and to eliminate the MSF errors of the visual optical grade mirrors without the need for post-processing.

Geometry-leveling and load-uniforming coupling control for the hyperstatic-legged platform by modeling its inherent properties

The hyperstatic-legged platform is the physical prototype for optical mirror support control. However, the hyperstatic problem leads to uncertainty in leg loads and platform attitudes, and current control schemes suffer from attitude oscillations and poor load controllability. This paper presents a geometry-leveling and load-uniforming coupling control method (G&LCC). Simulation comparisons of G&LCC with the point-chasing and fuzzy-control methods validate its unique ability to synchronously control platform attitudes with leg loads. Moreover, experiments based on a six-elastic-legged elastic platform demonstrate that only one to two iterations are required to adjust the attitudes to within 0.02°, while all leg loads converge to within 7% of expectations.

Design and application of omnidirectional mirror for catadioptric optical system dedicated to high-speed video registration of lightning

Omnidirectional optical mirrors are widely used in many scientific, industrial and military applications but there is still a lot to do to improve their projection characteristics. The paper presents design method for a novel class of omnidirectional mirrors characterized by their settable reflection angle and 3D/2D image projection. Such approach can effectively improve the mirrored image distribution on matrix of optical sensor. A complex mirror curvature was manufactured with application of computerized numerical control milling machines and Physical Vapor Deposition technique. Three prototypes with 15°, 30° and 45° vertical top view angles were tested. Mirrors were applied to get a set of wide range cloud-to-ground lightning video registrations. Analysis of the high-speed video confirmed design assumptions, and using lightning location system data, enabled dimensioning and measurement of the lightning channel geometry in 3D. Proposed method can be easily implemented in other applications involving omnidirectional observation and photogrammetry.

Enhanced molding and mechanical properties of SiC-based ceramic lattice structures via digital light processing

Silicon carbide (SiC) ceramic lattice structures (CLSs) hold significant potential for use in structural components and optical mirrors in space exploration due to their light weight, high strength, and excellent dimensional stability. However, they face challenges such as poor curing performance and weak mechanical strength during the digital light processing (DLP) additive manufacturing process. In this study, SiC@Al2O3 powder was prepared, resulting in a 21 % reduction in absorptivity compared to bare SiC powder. The ceramic paste derived from this powder achieved a curing thickness of up to 80 μm, exhibited a reduced over-curing width, and demonstrated a 75 % improvement in stability compared to bare SiC paste. Consequently, high-quality triply periodic minimal surfaces (TMPS) structured SiC@Al2O3 CLSs green bodies were successfully fabricated. By integrating precursor impregnation pyrolysis with the reaction melting infiltration (PIP-RMI) post-treatment densification method, SiC@Al2O3/Si CLSs were produced, exhibiting superior mechanical properties with low dimensional shrinkage. At 30 % volume fraction, the specific compressive strength of the primitive-TPMS SiC@Al2O3/Si CLSs reached 24.79 MPa. This study presents an effective method for fabricating SiC-based CLSs and establishes a foundation for the optimization of SiC ceramic fabrication processes.

Multiphysics Coupling Simulation of Off-Axis Integrated Cavity Optical Sensing System

The optical properties of an off-axis integrated cavity system are influenced by both structural deformation and thermal deformation. In this paper, the finite element simulation and analysis software COMSOL multiphysics was used to numerically simulate the optical system. By coupling geometric optics, solid mechanics, and solid heat transfer and conducting parametric temperature scanning, a multiphysics simulation of the off-axis integrated cavity optical sensing system was achieved. The effects of different temperature conditions on the stress field, displacement field, and optical mirrors were analyzed, and changes in optical properties were assessed using ray trajectories and point diagrams. Additionally, optical simulation software was used to simulate and optimize the experimental optical path, obtaining the distribution of light spots on the detector surface. This provides a theoretical basis for the subsequent optimization of the off-axis integrated cavity optical system.

Design and analysis of flexible tilt mirror driven by piezoelectric thin sheet actuators

Optical tilt mirrors (OTM) enable the mirrors to achieve high precision posture adjustment, playing a significant role in various optical system applications in the fields such as active optics, adaptive optics, satellite communications and biomedicines. However, the rapid development of modern technologies has brought new challenges to OTM in terms of their dimension, operating space and dynamic performance. Herein, a novel biaxial optical flexible tilt mirror (OFTM) driven by four simple bonded-type thin sheet piezoelectric actuators was proposed, where the OFTM was designed based on the flexible bending motions of composite piezoelectric beams. Particularly, OFTM is mainly composed of PZT sheet and stainless steel substrate, and shows a dimension of 42 mm × 42 mm × 0.2 mm. A theoretical model of OFTM was established to accurately describe the relationship between input electric field and output pose based on elastic beam theory, where the relationship was verified by both finite element analysis and experimental results. Finally, an OFTM prototype was fabricated and presented good performance on motion behaviors. Compared with traditional fast steering mirror (FSM) and MEMS mirror, the developed OFTM shows low cost, small size and simple manufacturing process, which greatly extends the applications of OFTTM in emerging fields.

The FastRICH ASIC for the LHCb RICH enhancements

The Ring-Imaging Cherenkov (RICH) detectors at LHCb have an excellent intrinsic time resolution due to the prompt Cherenkov radiation and focusing mirror optics. Novel RICH readout electronics, to be installed during the third Long Shutdown period (LS3) of the LHC, will introduce fast-timing information in the LHCb experiment. Central to the readout chain is a new application-specific integrated circuit (ASIC), called the FastRICH, with a unique set of features targeting operation in high-energy physics experiments and in particular the LHCb RICH detector.

A tour d'horizon of de Casteljau's work

Whilst Paul de Casteljau is now famous for his fundamental algorithm of curve and surface approximation, little is known about his other findings. This article offers an insight into his results in geometry, algebra and number theory.Related to geometry, his classical algorithm is reviewed as an index reduction of a polar form. This idea is used to show de Casteljau's algebraic way of smoothing, which long went unnoticed. We will also see an analytic polar form and its use in finding the intersection of two curves. The article summarises unpublished material on metric geometry. It includes theoretical advances, e.g., the 14-point strophoid or a way to link Apollonian circles with confocal conics, and also practical applications such as a recurrence for conjugate mirrors in geometric optics. A view on regular polygons leads to an approximation of their diagonals by golden matrices, a generalisation of the golden ratio.Relevant algebraic findings include matrix quaternions (and anti-quaternions) and their link with Lorentz' equations. De Casteljau generalised the Euclidean algorithm and developed an automated method for approximating the roots of a class of polynomial equations. His contributions to number theory not only include aspects on the sum of four squares as in quaternions, but also a view on a particular sum of three cubes. After a review of a complete quadrilateral in a heptagon and its angles, the paper concludes with a summary of de Casteljau's key achievements.The article contains a comprehensive bibliography of de Casteljau's works, including previously unpublished material.

Si-doped carbonized polymer dot as robust hydrophilic coating using for high efficiency antifogging

Hydrophilic coating can prevent surface from fogging but its application is limited by low mechanical performance. In this study, a hydrophilic coating was prepared by crosslinking the Si-doped carbonized polymer dot (Si-CPD) with 3-glycidyloxypropyltrimethoxysilane (GPTMS) and ethylene oxide (EO). The hydrophilic coating can be used as robust hydrophilic anti-fogging coating. The Si-CPD derived from ethylene diamine tetraacetic acid (EDTA) and aminopropyl oligosiloxanes (APOS) was successfully prepared via one-step hydrothermal method. Then, a resin solution was prepared by mixing Si-CPD, GPTMS and EO. Epoxy group of GPTMS and EO can react with amino group of Si-CPD. Finally, a composite coating with antifogging function can be obtained by simple heating curing. Due to the introduction of hydroxyl which derived from EO, the coating shows excellent antifogging performance. Meanwhile, the presence of inorganic component endows the coating with outstanding mechanical performance. The coating has great potential in related applications, such as optical lenses, mirrors and other transparency substrates.

Application of Wood's alloy for optical mirrors manufacturing

Application of Wood's alloy for optical mirrors manufacturing

Monolithic deformable mirror based on lithium niobate single crystal for high-resolution X-ray adaptive microscopy

X-ray microscopy is very promising not only for nondestructive and high-spatial-resolution observation of the internal structure of a sample but also for elemental distribution and chemical state analysis. However, the spatial resolution of microscopes remains unsatisfactory owing to the fabrication error in the objective lens. To realize an ultra-high-resolution, we propose and develop a monolithic deformable mirror based on a lithium niobite single crystal and a novel adaptive imaging system based on it. An X-ray interferometer confirmed that shape modification is possible with an accuracy of 0.67 nm in peak to valley under high stability (0.17 nm over 7 h) and hysteresis-free deformation control. Introducing this adaptive mirror into an X-ray microscope based on advanced Kirkpatrick-Baez mirror optics and correcting the wavefront aberration demonstrated that the X-ray image quality could be significantly improved.

Gravitational wave detection by hollow-core fiber-optics Mach-Zehnder interferometry

Recent advances in the field of very long distance optical communication suggest the adoption of the advanced technology based on Hollow Core Nested Anti- resonant Nodeless Fiber (HC-NANF) within the endeavour of Gravitational Wave detection using a Mach-Zehnder optical interferometer (MZ-IF). The proposal, consisting of a summary project of the device emphasizes the favorable properties of (MZ- IF) in comparison with Michelson Interferometer (M-IF) currently in operation. The key feature of the proposed method consists of the use of a couple of “fibrated” metallic antennas enfolded by a very large number (h x 7,7 x 104 with h= 1,2,3 etc.) of coiled rings or of straight sections of the (HC-NANF) fiber. This amounts to a corresponding fiber length: L (K) = h x 1500 Km. The relevant properties of the device are noise reduction, absence of critical optical mirror alignment in a noisy environment, reduced spatial extension of the apparatus, exploration of the entire sky scenario by freely orientable antennas, a substantial cost reduction of the apparatus. The remarkable properties of (HC-NANF), invented by F. Poletti in 2013 are currently investigated by his group at the University of Southampton, UK.

Neutron instrument concepts for a high intensity moderator at the European spallation source

In the course of the Horizon 2020 project HighNESS, a second moderator concept has been developed for the European Spallation Source, which complements the currently built moderator and is optimized for high intensity with a large viewable surface area. In this work we introduce conceptual designs for neutron instruments for condensed matter research designed to make optimal use of the capabilities of this moderator. The focus is on two concepts for small-angle neutron scattering and one neutron imaging instrument, which are intended to complement corresponding instruments that are already under construction at the European Spallation Source. One small-angle neutron scattering instrument concept resembles a conventional pinhole collimator geometry and aims to profit from the proposed second moderator by enabling to illuminate larger samples and providing particularly high resolution, drawing on a 30 m collimation and corresponding detector distance. A second small-angle neutron scattering instrument concept adopts nested mirror optics that enable to efficiently exploit the large moderator size and provide high resolution by focusing on the detector. The neutron imaging instrument concept is a typical pinhole instrument that can be found at continuous sources and draws on the corresponding strengths of high flux and large homogeneous fields-of-view, while still providing moderate wavelength resolution for advanced imaging methods.

Off-axis telescope misalignment correction based on defocus spot moment features

Optical mirror misalignments, which are caused by assembly mistakes and changes in the surrounding environment (such as gravity, temperature, and atmosphere), degrade the system’s imaging performance. Therefore, active misalignment correction is essential for ensuring the image quality of the off-axis telescope. In this paper, a novel misalignment correction method without wavefront sensors is proposed. The point spread functions (PSFs) of the system are analytically related to the optical mirror misalignments. On this basis, a fully connected neural network (FCNN) is used to establish the mapping relationship between the misalignments and the discrete orthogonal unbiased finite impulse response (UFIR) moment features, which can effectively characterize changes of intensity and geometric of the spot image. The simulation and experimental results in this paper justify the effectiveness and practicality of the proposed method. This approach offers a low-cost and straightforward technical method for achieving high imaging quality throughout the alignment and observation phases. This approach can prevent the accumulation of errors caused by wavefront detection and the high delay of multiple iterations.

Distortions of parabolic mirror optics for stereophonic lithography and prospects of compensations

The distortions of parabolic mirror optics used for stereophonic projection lithography were investigated. It has already been demonstrated that resist patterns are replicable on gently curved surfaces using mirror optics composed of faced paraboloids of revolution. However, it was found that replicated resist patterns were somewhat distorted from the original patterns. The distortions were caused by characteristics of projection optics. For this reason, the distortions were first calculated by tracing light rays. The calculation procedures are explained in detail. The calculated distortions almost coincide with the ones obtained by experiments. Next, the influences of distortions on the distributions of image intensity and replicated pattern widths were investigated. The maximum distortions reached 29% of the original size at the right-side corners of a 12 mm square, and the light intensity was lowered by 30%. For this reason, printed 200 μm pattern widths reached more than 500 μm on the right side. This was considered to be unfavorable for applying the method universally in various uses. For this reason, methods for compensating or modifying the optics distortions were investigated, and light intensity distributions were discussed.