Reflective Mirror Surface Research Articles

MULTI-SENSOR CAMERA MODEL FOR CONTROLLING COORDINATES OF POINTS ON THE SURFACE OF TELESCOPES

A new optoelectronic system for measuring the reflective mirror surface distortion of large telescopes is discussed in this study. This system comprises a multi-matrix structure of CMOS sensors, each sensor responsible for capturing an image of a control point on the mirror surface through a common objective. Simulation and calculation studies show that during operation, the position of the multi-sensor camera on the supporting ring is determined by control points on the telescope surface. The more control points, the higher the accuracy of the calculations. Simulation results indicate that the camera position error falls within acceptable limits when using 5 or more control points. Experimental results show that when calculating simultaneously with 3 control points, the error in determining the angular position of the camera reaches a value of  = 0.302 arc minutes, which is 2 - 2.5 times smaller than when calculating with only one control point.

X-ray mirror surface figure correction with nanometre precision controlled by layer stresses simulated by FEA.

Hard X-rays with energies higher than several kiloelectronvolts can be focused to spot sizes below 10 nm with the present synchrotron beamlines, offering unique advantages for the chemical, elemental and structure analysis of matter. Nevertheless, a surface precision on the nanometre scale for the focusing optics is required and remains the main hurdle limiting X-ray analytical techniques with single-nanometre spatial resolution. On the other hand, to preserve the wavefront properties of coherent X-ray beams, precise control of the reflective mirror surface quality at the nanometre scale is demanded for X-ray free-electron laser applications. In this work, the surface shape of a multilayer-coated X-ray mirror is controlled by layer stresses. The desired surface profile of the mirror is differentiated to its second order to obtain its corresponding curvature profile. With a step size of 1 mm along the mirror length, different coating thicknesses are applied to create different layer thermal stresses from uniform temperature change. The mirror surface profile can be obtained by integrating the curvature profile to its second order and further corrected by moving constant values for the slope and height. The technical process is simulated by finite element analysis (FEA). A case study showed that the residual slope error and the residual height error between the desired shape and the FEA result are 0.22 µrad (r.m.s.) and 1.42 nm (r.m.s.), respectively.

Effect of intermediate layers on atomic layer deposition-aluminum oxide protected silver mirrors

This work investigates intermediate materials deposited between silver (Ag) thin-film mirrors and an aluminum oxide (AlOx) barrier overlayer and compares the effects on mirror durability to environmental stresses. Physical vapor deposition of various fluorides, oxides, and nitrides in combination with AlOx by atomic layer deposition (ALD) is used to develop several coating recipes. Ag-AlOx samples with different intermediate materials undergo aggressive high-temperature (80°C), high-humidity (80%) (HTHH) testing for 10 days. Reflectivity of mirror samples is measured before and after HTHH testing, and image processing techniques are used to analyze the specular surface of the samples after HTHH testing. Among the seven intermediate materials used in this work, TiN, MgAl2O4, NiO, and Al2O3 intermediate layers offer more robust protection against chemical corrosion and moisture when compared with samples with no intermediate layer. In addition, results show that the performance of the ALD-AlOx barrier overlayer depends significantly on the ALD-growth process temperature. Because higher durability is observed in samples with less transparent TiN and NiO layers, we propose a figure of merit based on post-HTHH testing reflectivity change and specular reflective mirror surface area remaining after HTHH testing to judge overall barrier performance.

Analysis and experimental investigation for collimator reflective mirror surface deformation adjustment

Analysis and experimental investigation for collimator reflective mirror surface deformation adjustment

An integrated mirror and surface ion trap with a tunable trap location

We report a demonstration of a surface ion trap fabricated directly on a highly reflective mirror surface, which includes a secondary set of radio frequency (RF) electrodes allowing for translation of the quadrupole RF null location. We introduce a position-dependent photon scattering rate for a 174Yb+ ion in the direction perpendicular to the trap surface using a standing wave of retroreflected light off the mirror surface directly below the trap. Using this setup, we demonstrate the capability of fine-tuning the RF trap location with nanometer scale precision and characterize the charging effects of the dielectric mirror surface upon exposure to ultra-violet light.

Beam-clipping-induced diffraction effects in MEMS laser scanners for autostereoscopic outdoor displays

In micro-electro-mechanical systems (MEMS) laser scanners, the beams reflected by the micromachined mirror may be truncated at various edges in the system, e.g., due to finite size of the reflective mirror surface, at the rigid supporting mirror frame, and at the package of the light source. In this paper the joint effect of such individual beam clipping is described by introducing a so-called effective system aperture. Diffraction effects induced by this virtual aperture are analyzed by means of Fourier optics incorporating the Fraunhofer far field approximation. The beam clipping theory is then applied to a laser light module with integrated MEMS mirror for autostereoscopic outdoor displays. Employing an optimization of the MEMS mirror tilting angle with respect to the laser light source, the beam-clipping-induced diffraction effects are minimized.

Continuous color reflective displays using interferometric absorption

Reflective displays that rely on ambient light as opposed to an internal light source have been making inroads for a variety of important applications, especially those involving mobility where power usage must be aggressively controlled. The underlying color rendering strategies for both reflective and emissive displays have largely been the same, combining three fixed, primary color subpixels to compose the rich gamut that users expect. The result, for reflective color displays, is unfavorable brightness/gamut performance since each of the color subpixels absorbs roughly 2/3 of the incident white light. We demonstrate a new technology that we call the single mirror interferometric display that overcomes such limitations with pixels whose reflectance properties can tune through a continuum of colors, including high contrast black and white reflectance states. We use an effect that we call interferometric absorption in which a thin absorbing metal layer in front of a highly reflective mirror surface selectively absorbs different colors, depending on the gap that separates the two. The gap is controlled by electrostatic actuation in a relatively simple micro-electro-mechanical-system structure. We describe this elegant and powerful color rendering principle and present experimental results for the basic pixel device as well as early system demonstrations.

胶层固化对反射镜面形影响的仿真与试验

The effect of shrinkage stress induced by adhesive curing on a reflective mirror surface was analyzed when the thick adhesive layer was used to joint optical elements. Firstly, the principle of tensile stress induced by adhesive layer to optical elements during adhesive curing was analyzed and the main factors of generating shrinkage stress were obtained. Then, a finite element model of the reflective mirror set was constructed. The finite element analysis was carried out by using the thermal-to-shrinkage analogy and the thermal modeling tools were used to compute the adhesive curing shrinkage. The curing shrinkage was substituted by low temperature concentration, but the Coefficient of Thermal Expansion( CTE) value of the adhesive could not be taken place by the coefficient of adhesive shrinkage directly. After converting the coefficient of adhesive shrinkage to the equivalent CTE value, the analysis results are accord with the test results. Finally, the improved glue scheme was put forward on the basis of the analysis results. The experiment results indicate that the reflective mirror surface deformation( PV value) has decreased from 0.547 to 0.064, and the RMS value decreased from 0.127 to 0.038. This results mean that the effect of shrinkage stress in adhesive curing processing on the reflective mirror surface has improved greatly.

A continuous-membrane micro deformable mirror based on anodic bonding of SOI to glass wafer

As one of the most important components in adaptive optics, the deformable mirror (DM) is required to have a flat surface for better performance. For micromachined DMs, single-crystal-silicon (SCS) membrane is an ideal material for high quality reflective mirror surface owing to its good flatness and small residual stress. In this research, a process was established to realize SCS mirror membrane by DRIE of SOI wafer and anodic bonding of SOI wafer to Pyrex 7740 glass. Using this process, the proof-of-concept for a micromachined DM composed of SCS mirror surface has been successfully demonstrated. The prototype DM shows a stroke of 4.23 μm at 120 V. The P–V and rms of the reflective mirror surface are 492 and 82 nm, respectively. The performance of the prototype DM can somewhat satisfy the need of AO in visible spectrum. Better surface quality is anticipated by employing SOI wafers with strictly controlled residual stress.

Electrothermal micromirror with dual-reflective surfaces for circumferential scanning endoscopic imaging

We report the design, fabrication, and measurements of a dual-reflective, single-crystal silicon-based micromirror that can perform circumferential scanning for endoscopic optical coherence tomography (EOCT). Full 360-deg optical scan angle (OSA) can be achieved by using a dual-reflective mirror with ±45-deg (or 90-deg) mechanical scan angle (MSA), where each reflective mirror surface contributes a 180-deg optical scanning. A novel surface- and bulk-combined micromachining process based on silicon on insulator (SOI) wafers is developed for fabricating the dual-reflective micromirror. The mirror flatness is maintained by the single-crystal-silicon device layer of SOI wafers, and aluminum is coated on both sides for reflection. A fabricated device demonstrated about half circumferential scanning range at resonance of 425 Hz. Other measured data include the radii of curvature, −129 mm (front surface) and 132 mm (back surface), and the reflectance, 86.3% (front surface) and 84.2% (back surface). This micromirror has the potential to realize full-circumferential-scanning EOCT imaging.

Fabrication of Micro Tetrahedron Patterns Using Ultra-Precision Shaping System

Recently, ultra-precision machining of components and dies for information and communication industries, such as fresnel mirrors, diffraction lens, and die for super high intensity reflective sheet is one of the major target. To machine three-dimensional micro patterns, such as super high-intensity reflective sheets, ultra-precision and mirror surface fabrication processes are required. It has been reported, however, that continuous cutting, such as turning or shaping, is more suitable to ultra-precision machining. Many researchers have studied the manufacturing process of reflective sheet dies to obtain high form accuracy and surface quality. In this paper, ultra-precision shaping system was developed to fabricate micro patterns mechanically. In order to estimate performance of the shaping system, micro V-shaped grooves and tetrahedron pattern arrays for a super high intensity reflective sheet was applied. Also, a new measuring technology to inspect form and machining errors of a machined tetrahedron patterns was proposed. The results show that shaping system has a positioning accuracy of x, y, z axis with 100, 10, 10nm resolution, respectively. Micro V-shaped grooves could be machined at various depths and micro tetrahedron patterns with a good quality were obtained as well.

Single beam mapping of nonlinear phase shift profiles in planar waveguides with an embedded mirror

We demonstrate a technique for a single shot mapping of nonlinear phase shift profiles in spatial solitons that are formed during short pulse propagation through one-dimensional slab AlGaAs waveguides, in the presence of a focusing Kerr nonlinearity. The technique uses a single beam and relies on the introduction of a lithographically etched reflective planar mirror surface positioned in proximity to the beam's input position. Using this setup we demonstrate nonlinearity-induced sharp lateral phase variations for certain initial conditions, and creation of higher spatial harmonics when the beam is in close proximity to the mirror.