Field curvature correction in video endoscope lenses through the parameters of air meniscus

The research presents a method to synthesize lens data of an air meniscus built into the optical layout and acting as a correction element that fixes the field curvature of the entire optical system. The practical application of the proposed method is relevant when creating miniature lenses for medical video endoscopes when a small number of lenses and a flat image field for a CCD/CMOS sensor are important. Analytical dependencies for the lens data of the air meniscus are obtained and significant conditions for the field curvature correction are formed. A numerical example of a front stop lens design is demonstrated and confirms the correctness of the formulated conditions. A comparison of the aberration values of the original lens and an upgraded system is carried out. It is shown that, the values of the field curvature and astigmatism have been compensated as a result of introducing the synthesized parameters of the air meniscus into the optical layout. The correction is achieved while keeping the values of coma, distortion, focal length, and optical system total length at the level of the initial values.

MR-compatible optical microscope for in-situ dual-mode MR-optical microscopy

We present the development of a dual-mode imaging platform that combines optical microscopy with magnetic resonance microscopy. Our microscope is designed to operate inside a 9.4T small animal scanner with the option to use a 72mm bore animal RF coil or different integrated linear micro coils. With a design that minimizes the magnetic distortions near the sample, we achieved a field inhomogeneity of 19 ppb RMS. We further integrated a waveguide in the optical layout for the electromagnetic shielding of the camera, which minimizes the noise increase in the MR and optical images below practical relevance. The optical layout uses an adaptive lens for focusing, 2 × 2 modular combinations of objectives with 0.6mm to 2.3mm field of view and 4 configurable RGBW illumination channels and achieves a plano-apochromatic optical aberration correction with 0.6μm to 2.3μm resolution. We present the design, implementation and characterization of the prototype including the general optical and MR-compatible design strategies, a knife-edge optical characterization and different concurrent imaging demonstrations.

The Hard X-ray Nanoprobe beamline at Diamond Light Source

The Hard X-ray Nanoprobe beamline, I14, at Diamond Light Source is a new facility for nanoscale microscopy. The beamline was designed with an emphasis on multi-modal analysis, providing elemental mapping, speciation mapping by XANES, structural phase mapping using nano-XRD and imaging through differential phase contrast and ptychography. The 185 m-long beamline operates over a 5 keV to 23 keV energy range providing a ≤50 nm beam size for routine user experiments and a flexible scanning system allowing fast acquisition. The beamline achieves robust and stable operation by imaging the source in the vertical direction and implementing horizontally deflecting primary optics and an overfilled secondary source in the horizontal direction. This paper describes the design considerations, optical layout, aspects of the hardware engineering and scanning system in operation as well as some examples illustrating the beamline performance.

Impact of real mirror profiles inside a split-and-delay unit on the spatial intensity profile in pump/probe experiments at the European XFEL

For the High-Energy-Density (HED) beamline at the SASE2 undulator of the European XFEL, a hard X-ray split-and-delay unit (SDU) has been built enabling time-resolved pump/probe experiments with photon energies between 5 keV and 24 keV. The optical layout of the SDU is based on geometrical wavefront splitting and multilayer Bragg mirrors. Maximum delays between Δτ = ±1 ps at 24 keV and Δτ = ±23 ps at 5 keV will be possible. Time-dependent wavefront propagation simulations were performed by means of the Synchrotron Radiation Workshop (SRW) software in order to investigate the impact of the optical layout, including diffraction on the beam splitter and recombiner edges and the three-dimensional topography of all eight mirrors, on the spatio-temporal properties of the XFEL pulses. The radiation is generated from noise by the code FAST which simulates the self-amplified spontaneous emission (SASE) process. A fast Fourier transformation evaluation of the disturbed interference pattern yields for ideal mirror surfaces a coherence time of τc = 0.23 fs and deduces one of τc = 0.21 fs for the real mirrors, thus with an error of Δτ = 0.02 fs which is smaller than the deviation resulting from shot-to-shot fluctuations of SASE2 pulses. The wavefronts are focused by means of compound refractive lenses in order to achieve fluences of a few hundred mJ mm−2 within a spot width of 20 µm (FWHM) diameter. Coherence effects and optics imperfections increase the peak intensity between 200 and 400% for pulse delays within the coherence time. Additionally, the influence of two off-set mirrors in the HED beamline are discussed. Further, we show the fluence distribution for Δz = ±3 mm around the focal spot along the optical axis. The simulations show that the topographies of the mirrors of the SDU are good enough to support X-ray pump/X-ray probe experiments.

Spectroscopic Investigation of Nebular Gas (SING): general objectives and preliminary optical layout

Ультрафиолетовый спектральный диапазон (ближний УФ, 180-300 нм; дальний УФ, 115-180 нм) крайне востребован астрофизиками. Успешные космические проекты, такие как IUE, HST, GALEX, ASTROCAT/UVIT и другие, дали ученым совершенно новые данные для астрофизических исследований. Прямые УФ-изображения неба позволяют проследить морфологию протяженных объектов (планетарных туманностей, остатков сверхновых и т.д.), но эти данные дают очень ограниченную информацию о понимании физических условий (температура, плотность, поле излучения). Спектроскопические наблюдения позволяют изучать локальные физические условия, но обычно только в одной точке протяженной туманности. Спектроскопия, основанная на наблюдениях с помощью спектрографа с длинной щелью, позволяет объединить два этих метода. Для изучения динамики и эволюции протяженных объектов мы предлагаем такой инструмент - SING (Spectroscopic Investigation of Nebular Gas, спектроскопические исследования газа туманностей). Мы планируем установить его на борту китайской космической станции. В данной статье представлены общие задачи и предварительный оптический расчет прибора SING. The ultraviolet spectral subdiapasons, both near UV (180-300 nm) and far UV (115-180 nm), are highly requested by astrophysicists. The successful space missions like IUE, HST, GALEX and others provided scientists with absolutely new data for astrophysical studies. Direct UV images of the sky allow tracking the morphology of extended objects (planetary nebulae, supernova remnants etc), but these data provide very limited information about understanding the physical conditions (temperature, density, radiation field). Spectroscopic observations make it possible to study local physical conditions, but usually only at one point in an extended nebula. Spectroscopy that is based on long-slit spectrograph observations allow to combine these both. To study dynamics and evolution of extended objects we propose such an instrument SING (Spectroscopic Investigation of Nebular Gas). We plan to install it onboard the upcoming Chinese Modular Space Station (CSS). Here we describe general objectives and preliminary optical layout of the SING.

Lima or cima?

This paper outlines the construction of the corpus Alpenwort, a large, genre-based corpus of German texts on alpinism. We report on issues related to building the corpus from the Austrian Alpine Club Journal (1869–2010). First, a general description of our data and the project phases from digitization and annotation to publication is given. We focus on the most interesting challenges that the diverse layouts and the extensive use of Fraktur typefacing posed for optical layout recognition and optical character recognition (OCR) as well as post correction. The corrected data was lemmatized and annotated with part-of-speech information including named entities as well as TEI-conformant metadata. The resulting 19.9-million-word corpus is designed to be queried using CQPweb and Hyperbase and can be accessed freely online. Lastly, we give a short roadmap of current and future expansions and improvements as corpus data has been and is being enhanced in follow-up projects.

Focusing a round coherent beam by spatial filtering the horizontal source

This paper illustrates the use of spatial filtering with a horizontal slit near the source to enlarge the horizontal coherence in an experimental station and produce a diffraction-limited round focus at an insertion device beamline for X-ray photon correlation spectroscopy experiments. Simple expressions are provided to guide the optical layout, and wave propagation simulations confirm their applicability. The two-dimensional focusing performance of Be compound refractive lenses to produce a round diffraction-limited focus at 11 keV capable of generating a high-contrast speckle pattern of an aerogel sample is demonstrated. The coherent scattering patterns have comparable speckle sizes in both horizontal and vertical directions. The focal spot sizes are consistent with hybrid ray-tracing calculations. Producing a two-dimensional focus on the sample can be helpful to resolve speckle patterns with modern pixel array detectors with high visibility. This scheme has now been in use since 2019 for the 8-ID beamline at the Advanced Photon Source, sharing the undulator beam with two separate beamlines, 8-ID-E and 8-ID-I at 7.35 keV, with increased partially coherent flux, reduced horizontal spot sizes on samples, and good speckle contrast.