Development of single grating x-ray Talbot interferometer as a feedback loop sensor element of an adaptive x-ray mirror system

Taking advantage of the fact that an X-ray Talbot interferometer functions with X-rays of a broad energy bandwidth, high-speed X-ray phase tomography has been demonstrated by using white synchrotron light. Time resolution in addition to three-dimensional spatial resolution has been attained, and we report this achievement as the first four-dimensional (4D) X-ray phase tomography. Moire image movies of samples rotating at a speed of 1 or 2 rps generated by a Talbot interferometer were recorded at a frame rate of up to 1 kf/s, and differential phase image movies of the same frame rate were created by the Fourier-transform method. Consequently, a sub-second time resolution was achieved in the 4D phase tomography, while the spatial resolution was below 0.1 mm and 0.05 mm in axial and in-plane directions, respectively. An X-ray Talbot interferometer generates visibility images in addition to differential phase images, showing the distribution of microstructures, which cause ultra-small angle scattering but cannot be resolved individually with system spatial resolution. Tomographic image reconstruction from the visibility images was also demonstrated.

The recent use of a one-dimensional (1D) X-ray Talbot interferometer has triggered great interest in X-ray differential phase contrast imaging. As an improved version of a 1D interferometer, the development of two-dimensional (2D) grating interferometry strongly stimulated applications of grating-based imaging. In the framework of Fresnel diffraction theory, we investigated the self-image of 2D-phase gratings under partially coherent illumination. The fringe visibility of the self-image has been analyzed as a function of the spatial coherence length. From the viewpoint of self-image visibility, it is possible to find the optimal 2D grid for 2D X-ray grating interferometer imaging. Numerical simulations have been also carried out for quantitative evaluation. Results, in good agreement with theoretical analysis, indicate the spatial coherence requirements of the radiation illuminating a 2D grating interferometer. Moreover, our results can be used to optimize performances of a 2D grating interferometer and for further theoretical and experimental research on grating-based imaging systems.

An X-ray Talbot interferometer consisting of two capillary plates, which were used as X-ray amplitude gratings, was evaluated for X-ray phase imaging. A theoretical aspect of capillary X-ray Talbot interferometry is presented with a preliminary operation result using synchrotron radiation. A two-dimensional X-ray Talbot effect, or self-imaging effect, which was the basis of Talbot interferometry, was observed with the capillary plate, and moiré images formed by the X-ray Talbot interferometer exhibited contrasts corresponding to the differential phase shift caused by phase objects placed in front of the interferometer. Finally, the possibility of quantitative phase measurement with a fringe scanning technique is discussed.

The influence of polychromaticity of the X-ray source on the performance of an X-ray Talbot interferometer applied for phase-contrast imaging is analyzed through numerical simulations based on the Fresnel diffraction theory. The presented simulation results show that the visibility of the self-image is fairly insensitive to the source polychromaticity and explain why the interferometer could be well combined with polychromatic X-ray sources in recent experiments. Furthermore, the self-image with a high visibility can be obtained under polychromatic illumination even at a high-order fractional Talbot distance. This fact implies that the acquired image quality for phase measurements can be improved, since the primary signal for phase measurement is proportional to the inter-grating distance. Finally, we mention that the results are also valid for Talbot-Lau interferometer and scanning double-grating configuration.

The X-ray radiographic imaging technique is very important in medical, biological, inspection, material science, and other fields. However, it is not enough to obtain a clear X-ray image of samples with low absorbance materials, such as biological soft tissues. Then, we have used an X-ray phase-imaging method of an X-ray Talbot interferometer. In this method, X-ray gratings were required to have a narrow pitch and high aspect ratio structure. Therefore, we have developed and fabricated high-aspect-ratio X-ray gratings with a pitch of , a height of , and a large effective area of using X-ray lithography and narrow electroforming techniques. In this paper, we discuss the fabrication process of X-ray gratings with a narrow pitch and high-aspect-ratio structure, and results of X-ray phase tomography using an X-ray Talbot interferometer with these X-ray gratings.

The optical transfer function (OTF) is examined for an optical instrument corrected by an adaptive optics systems. A model introducing the application of modal control to the OTF and accounting for the effects of time lags and angular depointings is presented. The model allows the estimation of OTF decay in respect to the Fried diameter and for different time lags in an adaptive mirror. Modal control is described and delays in the controls of the adaptive mirror system are discussed.

The article analyzes the state of the problem of creating highly functional bionic prostheses and the relevance of creating an adaptive control system for such prostheses based on the results of biosignal processing is shown. The advantages and disadvantages of the method of direct signals registration from the motor departments of the human cerebral cortex, the use of specialized so-called nerve cuffs to receive signals directly from peripheral nerve fibers, as well as implanted electrodes and registration of surface electromyographic signals (sEMG) were considered. Taking into account the non-invasiveness, safety and simplicity of technical implementation, the sEMG registration method was used as the basis for the work of the designed system. However, to increase the informativeness of the source material and the possibility of isolating a greater number of informative signs of individual phantom movements, it is proposed to use a multi-electrode system, and to ensure the adaptability of the prosthesis, it is proposed to implement sensory feedback in the proposed control system structure. For this purpose, it is proposed to use signals from tactile sensors, which will be placed at the prosthesis fingers ends. The structure of the control system is proposed, which includes two related data exchange channels and four main elements: a multielectrode system with sEMG sensors; a stump-receiving sleeve with actuators; a smartphone or PC with appropriate software; a bionic prosthesis with a processor module, motor drivers and a module for registering tactile sensors signals. It is proposed to implement the main structural elements, such as the multielectrode system, the stump-receiving sleeve and the bionic prosthesis itself, as separate independent elements that are interconnected via separate wireless data exchange channels. The elements of the multielectrode system for recording sEMG and sensory feedback signals were developed.

The limitation of star detection in daytime is poor contrast of image. Compare with the strong sky background light, star signal is so weak that can’t be detected. There are some solutions to find star signal out from strong sky background, spectral filter is selected in this article. According to the different spectrum distributions of stars and sky background, different dead wavelengths is chosen to reduce the sky background light and increase the contrast between star object and sky background. Different kinds of spectral filters were placed between adaptive optical system and secondary mirror of 1.8m telescope in Lijiang observation station. The RMS value of wavefront correction residual error and the FWHM value of far-field light spot are chosen to evaluate the correction capability of AO system. Applying spectral filter, the RMS value is improved from 0.25λ to 0.17λ and the FWHM value is improved from 0.46 arc sec to 0.34 arc sec. Both of the evaluation criterions show that spectral filter is effective for detecting stars in daytime. Furthermore, it also makes it possible to apply our adaptive optics system in daytime in future.

We describe results from the first astronomical adaptive optics system to use multiple laser guide stars, located at the 6.5-m MMT telescope in Arizona. Its initial operational mode, ground-layer adaptive optics (GLAO), provides uniform stellar wavefront correction within the 2 arc minute diameter laser beacon constellation, reducing the stellar image widths by as much as 53%, from 0.70 to 0.33 arc seconds at lambda = 2.14 microns. GLAO is achieved by applying a correction to the telescope's adaptive secondary mirror that is an average of wavefront measurements from five laser beacons supplemented with image motion from a faint stellar source. Optimization of the adaptive optics system in subsequent commissioning runs will further improve correction performance where it is predicted to deliver 0.1 to 0.2 arc second resolution in the near-infrared during a majority of seeing conditions.

The performance of high-contrast AO instruments (GPI, SPHERE, ScEXAO, MagAO) and other systems that operate at visible wavelengths can be severely hampered by control system latencies and temporal wavefront errors. In high-contrast systems, temporal errors and delays are manifest as high spatial frequency wavefront residuals that scatter light into the controllable region of the PSF and diminish contrast, an effect that is particularly severe when atmospheric coherence times are short. Solutions that have been proposed include lower latency electronics, deformable mirrors with lower mechanical response times, and specialized control algorithms such as predictive control. These advancements will be necessary for achieving the latency goals of high actuator count systems on future Extremely Large Telescopes (ELTs), including NFIRAOS+ and PFI on the Thirty Meter Telescope, upgrading the performance of existing highcontrast systems, and pushing adaptive optics to visible wavelengths. LLAMAS (Low-Latency Adaptive Optical Mirror System) is a fully funded adaptive optics system at the Lawrence Livermore National Laboratory site that will test these techniques in an integrated, real time, closed-loop AO system. With a total system latency goal of ~100 microseconds (including mechanical response time, not including frame integration), LLAMAS will achieve an order of magnitude improvement in AO system latencies over the current generation of high-contrast AO systems. The woofer/tweeter architecture will incorporate a 492-actuator Boston Micromachines MEMS device mapping 24 actuators across a circular pupil. The tweeter mirror will be paired with a specialized low-latency driver, delivering less than 40 microseconds electronic and mechanical latency (10 – 90%). The real-time control computer will utilize the computationally efficient Fourier Transform Reconstructor with a predictive Kalman filter with a goal of completing all computations and reconstructing the wavefront in less than 20 microseconds. LLAMAS will be fully integrated with a 21×21 lenslet Shack-Hartmann sensor by January 2019. These proceedings describe the LLAMAS design, characterize the performance of its low-latency componentry, and discuss the relevance of the design for future high-contrast, visiblelight, and high actuator count AO systems on ELTs.

MAPS, MMT Adaptive optics exoPlanet characterization System, is the upgrade of legacy 6.5m MMT adaptive optics system. It is an NSF MSIP-funded project that includes (i) refurbishing of the MMT Adaptive Secondary Mirror (ASM), (ii) new high sensitive and high spatial order visible and near-infrared pyramid wavefront sensors, and (iii) the upgrade of Arizona Infrared Imager and Echelle Spectrograph (ARIES) and MMT high Precision Imaging Polarimeter (MMTPol) science cameras. This paper will present the design and development of the visible pyramid wavefront sensor. This system consists of an acquisition camera, a fast-steering tip-tilt modulation mirror, a double pyramid, a pupil imaging triplet lens, and a low noise and high-speed frame rate based CCID75 camera. We will report on hardware and software and present the laboratory characterization results of the individual subsystems, and outline the on-sky commissioning plan.

A wide-field adaptive optics system based on an adaptive secondary mirror (ASM) is one of a future plan for the next-generation Subaru adaptive optics system. The main application of ASM based AO will be a groundlayer adaptive optics (GLAO) with field-of-view larger than 10 arc minutes. The high Strehl-ratio of on-source correction by high-order ASM (expected to be about 1000) and the reduction of emissivity are also attractive points. In this paper, we report a preliminary result of simulations for the these applications of ASM to study conceptual design of the next-generation wide-field Subaru adaptive optics.

The paper reviews advanced process for manufacturing high-precision optical components used in space-based electrooptic systems for scientific research and Earth remote sensing. It presents an integrated process for automatic shaping (TESAF) of aspheric surfaces, including off-axis surfaces, of optical elements for electrooptic systems. This paper discusses various methods for shaping optical parts with virtually any degree of asphericity and various values of the off-axis parameter (off-axis aspherics) achieving surface shape precision to within λ/60…λ/80 (λ = 0.6328 micron) by the standard deviation criteria. The paper also presents the newly developed off-axis collimators, designed to shape a reference wavefront within a broad spectral range from ultraviolet to infrared radiation. In particular, a mirror collimator with an adaptive off-axis mirror that is capable of changing the wavefront that is being formed in order to obtain the response function of the electrooptical system under study. Optical systems built using the TESAF process are already successfully used. Key words: surface shaping, aspheric surface, surface interferogram, standard deviation.

The behavior and operation of integrated assemblies comprised of arrays of active transducers interfaced with complex cast compliant structures depends on their true structural dynamics. Such assemblies are characteristic of control elements for adaptive optical systems, sonar systems, and other continuously deformable structures in which energy and motion are transmitted through complex compliant materials. The mechanical and physical interfaces between active transducers and their supporting and radiating structures relate directly to their dynamics.Sophisticated bonding and processing of compliant and rigid materials in such complex assemblies determine their operational parameters. Understanding the effects of structural anomalies and defects is of critical importance to insuring correct array operation, and a non-destructive method for the visualization of anomalous structural and material characteristics would be of great value in both development and testing of such systems. Also, mechanisms for acoustic and mechanical energy transfer through these structures into adjoining media can be inferred from such visualizations. Holographic interferometry presents itself as a viable and useful method for the non-destructive realization of this type of information.The behavior and operation of integrated assemblies comprised of arrays of active transducers interfaced with complex cast compliant structures depends on their true structural dynamics. Such assemblies are characteristic of control elements for adaptive optical systems, sonar systems, and other continuously deformable structures in which energy and motion are transmitted through complex compliant materials. The mechanical and physical interfaces between active transducers and their supporting and radiating structures relate directly to their dynamics.Sophisticated bonding and processing of compliant and rigid materials in such complex assemblies determine their operational parameters. Understanding the effects of structural anomalies and defects is of critical importance to insuring correct array operation, and a non-destructive method for the visualization of anomalous structural and material characteristics would be of great value in both development and testing of such systems. Also, mechanisms for ac...

Differential phase-contrast (DPC) X-ray imaging has been performed in the Talbot-Lau configuration, in which the X-ray source was a combination of an absorption grating and a laboratory X-ray generator. We report here quantitative analysis of partial coherence effects on the X-ray Talbot-Lau interferometer. Based on the visibility of the self-image, the well-known geometry condition is reproduced. It is shown that effects of partial coherence are determined by the opening ratio of the source grating, and that the effects are independent of the Talbot order and the type of the phase grating, a condition quite different from those in a Talbot interferometer. A possible explanation is discussed from the point of view of the effective spatial coherence length. Taking into account the available X-ray flux and experimental fluctuations, we present the optimum opening ratio. Furthermore, we mention that our results can also be successfully used to discuss the properties of a multiline X-ray source.