This PDF file contains the front matter associated with SPIE Proceedings Volume 10151, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

Applications, which can profit from holographic 3D displays, are the visualization of 3D data, computer-integrated manufacturing, 3D teleconferencing and mobile infotainment. However, one problem of holographic 3D displays, which are e.g. based on space bandwidth limited reconstruction of wave segments, is to realize a small form factor. Another problem is to provide a reasonable large volume for the user placement, which means to provide an acceptable freedom of movement. Both problems should be solved without decreasing the image quality of virtual and real object points, which are generated within the 3D display volume. A diffractive optical design using thick hologram gratings, which can be referred to as Bragg diffraction based volume gratings, can provide a small form factor and high definition natural viewing experience of 3D objects. A large collimated wave can be provided by an anamorphic backlight unit. The complex valued spatial light modulator add local curvatures to the wave field he is illuminated with. The modulated wave field is focused onto to the user plane by using a volume grating based field lens. Active type liquid crystal gratings provide 1D fine tracking of approximately ± 8° deg. Diffractive multiplex has to be implemented for each color and for a set of focus functions providing coarse tracking. Boundary conditions of the diffractive multiplexing are explained. This is done in regards to the display layout and by using the coupled wave theory (CWT). Aspects of diffractive cross talk and its suppression will be discussed including longitudinal apodized volume gratings.

We present recent progress in design of innovative versatile laser head for lasers based on thin-disk architecture which are being constructed at the HiLASE centre of the IOP in the Czech Republic. Concept of thin-disk laser technology allows construction of lasers providing excellent beam quality with high average output power and optical efficiency. Our newly designed thin-disk carrier and pump module comes from optical scheme consisting of a parabolic mirror and roof mirrors proposed in 90’s. However, mechanical parts and a cooling system were in-house simplified and tailor-made to medium power lasers since no suitable setup was commercially available. Proposed opto-mechanical design is based on stable yet easily adjustable mechanics. The only water nozzle-cooled component is a room-temperature-operated thindisk mounted on a special cooling finger. Cooling of pump optics was replaced by heat conductive transfer from mirrors made of special Al alloy to a massive brass baseplate. Such mirrors are easy to manufacture and very cheap. Presented laser head was manufactured and tested in construction of Er and Yb doped disk lasers. Details of the latest design will be presented.

This paper treats the issue of locking a solid state laser, pumped by high power diodes (Verdi V5), to a twenty meter long optical resonator for OSQAR LSW - light shining through the wall, dark matter search experiment. In this paper the optical design and a possible locking scheme are presented. The environmental conditions in SM18 testing hall at CERN, where OSQAR experiment is based, are discussed. The main focus is put on the vibration analysis, cavity transversal modes behaviour, possible clipping in the anticryostat of LHC – Large Hadron Collider magnet bore and locking loop parameters required for future experimental testing. The expected finesse of resonator will be presented and discussed in the sense of OSQAR LSW; its impact on possible new exclusion limits is discussed.

Compressed sensing (CS) is a branch of computational optics able to reconstruct an image (or any other information) from a reduced number of measurements – thus significantly saving measurement time. It relies on encoding the detected information by a random pattern and consequent mathematical reconstruction. CS can be the enabling step to carry out imaging in many time-consuming measurements. The critical step in CS experiments is the method to invoke encoding by a random mask. Complex devices and relay optics are commonly used for the purpose. We present a new approach of creating the random mask by using laser speckles from coherent laser light passing through a diffusor. This concept is especially powerful in laser spectroscopy, where it does not require any complicated modification of the current techniques. The main advantage consist in the unmatched simplicity of the random pattern generation and a versatility of the pattern resolution. Unlike in the case of commonly used random masks, here the pattern fineness can be adjusted by changing the laser spot size being diffused. We demonstrate the pattern tuning together with the connected changes in the pattern statistics. In particular, the issue of patterns orthogonality, which is important for the CS applications, is discussed. Finally, we demonstrate on a set of 200 acquired speckle patterns that the concept can be successfully employed for single-pixel camera imaging. We discuss requirements on detector noise for the image reconstruction.

In this article we present an algorithm for automatic road edge detection from MLS (Mobile Laser Scanning) data. The method takes advantage of linear structures derived from MLS point clouds. These lines are extracted from the point cloud and grouped following geometric restrictions. Then, the outlines of the groups are extracted as road edges. Finally, a moving window filter is applied to those points in order to remove outliers and delineate the road edge. The method was tested on an 800m stretch of road, and the results were checked through visual inspection. Correctness and completeness were 99.1% and 97.5%, respectively.

The process of ultrasonic machining is especially used for brittle hard materials as the additional ultrasonic vibration of the tool at high frequencies and low amplitudes acts like a hammer on the surface. With this technology it is possible to drill holes with lower forces, therefor the machining can be done faster and the worktime is much less than conventionally. A three-axis dynamometer was used to measure the forces, which act between the tool and the sample part. A focus is set on the sharpness of the tool. The results of a test series are based on the Sauer Ultrasonic Grinding Centre. On the same machine it is possible to drill holes in the conventional way. Additional to the ultasonic Input the type an concentration of coolant is important for the Drilling-force. In the test there were three different coolant and three different concentrations tested. The combination of ultrasonic vibration and the right coolant and concentration is the best way to reduce the Forces. Another positive effect is, that lower drilling-forces produce smaller chipping on the edge of the hole. The way to reduce the forces and chipping is the main issue of this paper.

Plasma mirrors have become an important tool in high power laser physics due to their ability to suppress laser pre-pulses and amplified spontaneous emission allowing a cleaner and sharper rising edge pulse to be focused onto a target. A PMMA ellipsoidal plasma mirror used to increase the peak intensity of a high power laser pulses before it reaches the target is presented. The ellipse has been designed to increase by a factor 3, between input and output, the F-number of the beam, inducing in theory a factor 9 gain in peak intensity. Diamond machining, which is a technique capable of producing sub-micron accuracy on steep, freeform surfaces, is an ideal process for manufacturing these types of mirrors. In this paper, we discuss the diamond machining requirements to manufacture such near diffraction limited high numerical aperture mirrors.

Monitoring displacements on some structures such as large bridges is essential to study their structural performance in order to avoid severe damage or even their collapse. In this work, we use images obtained with digital video cameras to estimate the displacements of a metallic bridge by means of cross-correlation. Thus, it was possible to detect millimetric displacements for distances between the camera and the bridge upper ten meters. In order to obtain a better representation of the structural displacements along the bridge and its modal shapes, a technique of video magnification was also applied. The results obtained show that the combination of both techniques can provide relevant information for a structural analysis of the bridge.

The ultra-hydrophobic surfaces have the prospect of great importance in industry, both in applications demanding easy cleaning, and they are presumed to reduce loss when the active parts of hydraulic machines are treated. Interaction of fluids with ultra-hydrophobic surface is accompanied by creation of layer of air, so called air film, which depends on the quality of the surface. The quality of the surface is influenced by the matrix roughness, the character of physical or chemical cover. This properties lead to monolithic air layer presented as air film, or lead to plurality of bubbles of various sizes seated upon the surface. The air film can be observed visually at sufficient magnification and the dynamic interaction between fluid flow and air film can be studied with Global Imaging methods, particularly Particle Image Velocimetry (PIV). There is the velocity profile in the vicinity of the air film in the main interest of the research. Here we present the visualization of air film depending on Reynolds number of flowing liquid.

A new surface metrology instrument, the ‘Swinging Part Profilometer’ (SPP), has been developed for in-situ measurement of optics undergoing robot-processing in the ground (non-specular) state. In this paper, we present the hardware-design of the SPP, together with software for hardware-control, data-acquisition and surface-reconstruction. First results on a sample part are presented, compared with interferometric metrology, and error-contributions considered. Notably, during each individual scan of a measurement-cycle, the probe remains fixed. This lends itself to automated probe-deployment by the same robot as performs surface-processing, as probe stability is required on only the time-scale for a single scan.

This paper deals with the qualification of a 3D structured light scanning system for an application of reverse engineering of a mechanical part. As this white light scanner is an electro-optical device and based on the principle of optical triangulation, the measurement accuracy is affected by the measured part geometry and its position within the scanning window. The effects of the scan depth and the projected angle, characterizing the surface normal of the measured surface to the scanning point of view, on the measurement of accuracy are not considered in the standard calibration process of manufacturers and have been identified by experiments in the present work. The digitization errors are analyzed and characterized thanks to a measurement protocol based on quality indicators. Theses quality indicators are evaluated thanks to simple calibrated artifacts. The aim of this work is to redefine the ideal relative distance and relative angle for minimizing the digitizing errors in relation to those stated by the manufacturer for a reverse engineering application.

As applications for freeform optics continue to grow, the need for high-precision metrology is becoming more of a necessity. Currently, coordinate measuring machines (CMM) that implement touch probes or optical probes can measure the widest ranges of shapes of freeform optics, but these measurement solutions often lack sufficient lateral resolution and accuracy. Subaperture stitching interferometry (SSI™) extends traditional Fizeau interferometry to provide accurate, high-resolution measurements of flats, spheres, and aspheres, and development is currently on-going to enable measurements of freeform surfaces. We will present recent freeform metrology results, including repeatability and cross-test data. We will also present MRF® polishing results where the stitched data was used as the input “hitmap” to the deterministic polishing process.

A number of soft x-ray / water window laboratory sources is being developed by many groups including the group at CTU. This paper presents simulations and critical parameter estimates for lensless imaging using the laboratory sources, especially the capillary discharge source being developed by our group.¹ Water window lensless imaging is demonstrated to be generally feasible with high repetition laboratory sources.

The entry of CNC machining processes into optics brought the possibility of nearly arbitrary shape generation. Obviously the measurement of the generated shape increasingly gains the importance, because the generation has to be performed in an iterative manner as the required precision increases. Often mid spatial frequency error is neglected because it is not an easy task to be measured. Unfortunately those unwanted residual deviation in a shape left after grinding could dramatically complicate a subsequent polishing procedure. Mid spatial frequency content if not controlled well could spoils significantly the performance of the optical system. Elimination of mid spatial residuals originated in grinding process is nearly impossible or very difficult by sub-aperture polishing. Hence it is important to measure the grinded surface with sufficient lateral resolution. Tactile probes (usually used for shape measurement of grinded surfaces) can measure with sufficient lateral resolution but only at the expense of time. Interferometer based techniques fail when applied to scattering surfaces due to speckles. The authors have proposed multi-wavelength multi-directional digital holography – the method perfectly suitable for grinded surfaces shape measurement. Naturally, reconstructed phase maps are affected by speckle noise implying significant errors in the calculation of the shape of the surface. In order to reduce the effect of speckle noise and hence to increase the sensitivity of the measurement of the grinded surface shape, we propose to apply windowed digital holography. This paper describes the principle of the windowed digital holography and the way of straightforward application of the method in shape measurement of grinded surfaces.

The demands on the quality of large aperture spherical and mild aspheric optical surfaces continue to rise in modern optical systems. Due to the aperture size of these surfaces measuring of their shape is quite problematic. One of the ways to measure these surfaces is the subaperture stitching interferometry. Its accuracy is highly depended on lattice design and accuracy of the positioning system. Optimal lattice design in relation to transmission element applied in interferometer together with coordinates calculation for the positioning system for measuring individual subapertures is the subject of this paper. To set the required orientation and position of the optical surface relative to the interferometer positioning system with six degrees of freedom was used. Three of them were realized as prismatic kinematic pairs and remaining three as revolution joints. In this paper the choice of coordinate systems for individual axes of the positioning system together with inverse kinematics used for setting the correct position and orientation of the optical surface are described.

An interferometer has been used to measure the surface profile of generic object. Frequency scanning interferometry has been employed to provide unambiguous phase readings, to suppress etalon fringes, and to supersede phase-shifting. The frequency scan has been performed in three narrow wavelength bands, each generated by a temperature tuned laser diode. It is shown, that for certain portions of measured object, it was possible to get absolute phase measurement, counting all wave periods from the point of zero path difference, yielding precision of 2.7nm RMS over 11.75mm total path difference. For the other areas where steep slopes were present in object geometry, a relative measurement is still possible, at measured surface roughness comparable to that of machining process (the same 2.7nm RMS). It is concluded, that areas containing steep slopes exhibit systematic error, attributed to a combined factors of dispersion and retrace error.

Laser technologies such as welding and cutting rely on process gases. We suggest to use schlieren imaging to visualize the gas flow during these processes. During the process of laser welding, the shielding gas flows to the welded area to prevent oxidation of the weld pool by surrounding air. The gas also interacts with hot plasma spurting from the key hole induced by the laser beam incident on the molten material. This interaction is quite complicated because hot plasma mixes with the cold shielding gas while the system is moving along the weld. Three shielding gases were used in the presented experiment: Ar, He and N2. Differences in dynamics of the flow are clearly visible on schlieren images. Moreover, high speed recording reveals a structure consisting of hot gas bubbles. We were also able to determine the velocity of the bubbles from the recording. During laser cutting, the process gas flows coaxially with the laser beam from the nozzle to remove the molten material out of the kerf. The gas flow is critical for the quality of the resulting edge of the cut. Schlieren method was used to study gas flow under the nozzle and then under the material being cut. This actually creates another slot nozzle. Due to the very low speed of flow below the material the schleiren method is already at the limit of its sensitivity. Therefore, it is necessary to apply a differential technique to increase the contrast. Distinctive widening of the flow shaped by the kerf was observed.

We report on the development and implementation of the digital holographic tomography for the three-dimensio- nal (3D) observations of the domain patterns in the ferroelectric single crystals. Ferroelectric materials represent a group of materials, whose macroscopic dielectric, electromechanical, and elastic properties are greatly in uenced by the presence of domain patterns. Understanding the role of domain patterns on the aforementioned properties require the experimental techniques, which allow the precise 3D measurements of the spatial distribution of ferroelectric domains in the single crystal. Unfortunately, such techniques are rather limited at this time. The most frequently used piezoelectric atomic force microscopy allows 2D observations on the ferroelectric sample surface. Optical methods based on the birefringence measurements provide parameters of the domain patterns averaged over the sample volume. In this paper, we analyze the possibility that the spatial distribution of the ferroelectric domains can be obtained by means of the measurement of the wavefront deformation of the transmitted optical wave. We demonstrate that the spatial distribution of the ferroelectric domains can be determined by means of the measurement of the spatial distribution of the refractive index. Finally, it is demonstrated that the measurements of wavefront deformations generated in ferroelectric polydomain systems with small variations of the refractive index provide data, which can be further processed by means of the conventional tomographic methods.

Eliminating back reflections is critical in the design of a fundus camera with internal illuminating system. As there is very little light reflected from the retina, even excellent antireflective coatings are not sufficient suppression of ghost reflections, therefore the number of surfaces in the common optics in illuminating and imaging paths shall be minimised. Typically a single aspheric objective is used. In the paper an alternative approach, an objective with all spherical surfaces, is presented. As more surfaces are required, more sophisticated method is needed to get rid of back reflections. Typically back reflections analysis, comprise treating subsequent objective surfaces as mirrors, and reflections from the objective surfaces are traced back through the imaging path. This approach can be applied in both sequential and nonsequential ray tracing. It is good enough for system check but not very suitable for early optimisation process in the optical system design phase. There are also available standard ghost control merit function operands in the sequential ray-trace, for example in Zemax system, but these don’t allow back ray-trace in an alternative optical path, illumination vs. imaging. What is proposed in the paper, is a complete method to incorporate ghost reflected energy into the raytracing system merit function for sequential mode which is more efficient in optimisation process. Although developed for the purpose of specific case of fundus camera, the method might be utilised in a wider range of applications where ghost control is critical.

This article presents the visualization of the cavitation bubble generated with laser-induced breakdown. The cavitation bubble is generated with 532nm Nd: YAG laser beam, 10ns short with two different optical setups. Here, we use direct optical way focusing the laser beam, and reverse way base on the focusing mirror. We are using different laser light power and visualize the laser probe in correlation of bubble characteristics. The visualization is set on long-distance microscopy and shadowgraph lightening method. The main goal of the research is to set the optical setup for the laserinduced breakdown and to create the calibration relation curve for the bubble size dependence on the input energy of the laser beam. This calibration curve is related to the lifespan of each bubble, or the group of bubbles.

Lead zirconate titanate (Pb[Zr_xTi_1-x]O₃ ) is well-known for his excellent ferroelectric, piezoelectric and electromechanical properties. These properties are closely related to the perovskite crystal structure of PZT. A common way to achieve thin film of perovskite PZT is to anneal the layer after deposition. The high annealing temperature (600 – 700°C) limits a set of usable substrates. To grow a thin layer of perovskite PZT at reduced temperature it is necessary to add crystallization energy to the system by another way. In this article are presented some results of using ion beam sputtering system (IBS) with ion beam assistance (IBAD) to growth perovskite PZT layer at reduced temperature. This process is very complicated and the resulting layer properties are strongly influenced by deposition parameters (ions energy, chemical composition of the atmosphere in the sputtering chamber etc.). We achieved partial success when pyrochlore crystal structure of PZT was grown at reduced substrate temperature (110°C) (at this temperatures are the PZT layers usually amorphous)

Spectrum of light which is emitted or reflected by an object carries immense amount of information about the object. A simple piece of evidence is the importance of color sensing for human vision. Combining an image acquisition with efficient measurement of light spectra for each detected pixel is therefore one of the important issues in imaging, referred as hyperspectral imaging. We demonstrate a construction of a compact and robust hyperspectral camera for the visible and near-IR spectral region. The camera was designed vastly based on off-shelf optics, yet an extensive optimization and addition of three customized parts enabled construction of the camera featuring a low f-number (F/3.9) and fully concentric optics. We employ a novel approach of compressed sensing (namely coded aperture snapshot spectral imaging, abbrev. CASSI). The compressed sensing enables to computationally extract an encoded hyperspectral information from a single camera exposition. Owing to the technique the camera lacks any moving or scanning part, while it can record the full image and spectral information in a single snapshot. Moreover, unlike the commonly used compressed sensing table-top apparatuses, the camera represents a portable device able to work outside a lab. We demonstrate the spectro-temporal reconstruction of recorded scenes based on 90×90 random matrix encoding. Finally, we discuss potential of the compressed sensing in hyperspectral camera.

The aim of this work is an exploration of the options for optical surface polishing using the Zeeko IRP 100 machine and raster kinematics suitable for free-form polishing. For this purpose, aspheric surfaces were polished in raster prepolishing mode and then in Precession raster 3D shape correction, which is based on the Dwell time tool movement control. It was found that shape accuracy can achieve the value of approximately 35 nm RMS. The main inaccuracy was caused by the mid-spatial frequencies generated by the kinematics of the applied tools, which also limited the achievable values of microroughness.

High demands on the final surfaces micro-roughness as well as great shape accuracy have to be achieved under the manufacturing process of the precise mirrors for Metis orbital coronagraph. It is challenging engineering task with respect to lightweight design of the mirrors and resulting objectionable optical surface shape stability. Manufacturing of such optical elements is usually affected by number of various effects. Most of them are caused by instability of temperature field. It is necessary to explore, comprehend and consequently minimize all thermo - mechanical processes which take place during mirror cementing, grinding and polishing processes to minimize the optical surface deformation. Application of FEM simulation was proved as a useful tool to help to solve this task. FEM simulations were used to develop and virtually compare different mirror holders to minimize the residual stress generated by temperature changes and to suppress the shape deformation of the optical surface below the critical limit of about 100 nm.

The measurement of spatially varying surface reflectance is required for faithful reproduction of real world to allow for predictive look of computer generated images. One such proposed method uses a rotational kaleidoscopic imaging, where illumination and imaging paths are realized by subimages on kaleidoscopic mirrors and illumination is carried out by a DLP projector. We describe a novel geometric calibration method for a rotational kaleidoscope that is necessary to get aligned and accurate data from measurement. The calibration has two stages. The first stage mechanically adjusts the camera, the projector, and the autocollimator against the kaleidoscope mirrors. The second stage is based on the software. By random perturbation of camera and projector in corresponding mathematical model of the kaleidoscope we estimate better real positions of camera and projector in a physical setup, comparing the computed images from the software simulator and the acquired images from the physical setup.

This paper deals with optical losses in the coatings consisting of a combination of titanium dioxide (TiO₂) and silicon dioxide (SiO₂) layers evaporated by the ion beam assisted deposition (IBAD). This combination is commonly used for optical coatings as a standard choice for antireflective or any other optical filter in the visible and near IR range. Although the technology has been known for decades, we point out that some undescribed parasite losses can still appear and we show how to deal with them. In fact, in some cases, the losses made the target coating even inapplicable. In this paper we try to investigate the origin of the losses and we describe the deposition parameters which allow us to reduce or completely remove them. We determined whether the losses are proportional to the total thickness of the coating or to the number of layers. The influence of scattering was measured as well. Deposition parameters which were studied are the substrate temperature, discharge voltage of the assisting ion gun, oxygen flow of the assisting ion gun and the deposition rate, especially its starting curve. Influence of the post process annealing was studied as well. Starting curve of the deposition rate of SiO₂ layer and the amount of oxygen flowing through the assisting ion gun were found as a crucial parameters.

Lead zirconate titanate (PZT) is widely used for its ferroelectric and piezoelectric properties, which are conditioned by perovskite structure. Crystallization into this desired phase is determined also by a proper stoichiometry, where the lead concentration is a crucial parameter. The crystallization process takes place during annealing under high temperatures, which is linked to heavy lead losses, so the lead has to be in excess. Therefore, this paper is devoted to the control of chemical composition of PZT thin films deposited via ion beam sputtering (IBS). A commonly used approach for IBS relies on employing a multicomponent target to obtain films with the same composition as that of the target. However, in the case of PZT it is favorable to have the ability to controllably change the chemical composition of thin films in order to acquire high perovskite content. Our study revealed that the determinative lead content in PZT layers prepared by simple and dual ion-beam deposition from a multicomponent target can be easily controlled by the power of primary ion source. At the same time, the composition is also dependent on the substrate temperature and the power of assistant ion source. Thin PZT films with more than 30 % lead excess were acquired from a stoichiometric multicomponent target (i.e. a target without any lead excess). We can therefore propose several possible sets of deposition parameters suitable for the PZT deposition via IBS to obtain high perovskite content.

This paper deals with the development of a broadband antireflective coating for a special optical components for the NEOSTED project by European Space Agency (ESA). The aim of this work was to find a suitable design of the optical coating and to develop its production process so it meets the main requirement in which the average reflectance of the coating must be under 0.5 % for wavelengths in the range of 470 - 770 nm. The combination of titanium dioxide (TiO₂) and silicon dioxide (SiO₂) prepared by the ion beam assisted deposition (IBAD) was chosen for practical experiments and finally for the production as well. The final decision among the proposed designs and materials involved especially the number of layers used in the design in combination with the thickness control technology. From preproduction tests it turned out that the quartz monitor with the thickness set point correction based on a post process measurement is suitable for controlling deposited thickness in the application. This paper presents data from the preproduction tests and data from the first part of the production. A homogeneity of the deposited layer thickness was evaluated based on the measurement of the thickness across the sample.

The work deals with the creation of correction data when generating spherical and aspherical surfaces. Generation is performed on the converted 5-axis milling machine, for which it is necessary to generate control programs. In the process of generating surfaces may be formed random errors. Hence the need to measure workpieces, and errors corrected. There is thus solved a measurement of generated surface on coordinate measuring machine Mitutoyo LEGEX 744 and draft methods of data processing by using polynomial of nth order. The measured data are processed by Matlab, specifically CFTool module. This method is further tested and subsequently the experiment evaluated.

This article describes the mounting system of lenses in a coronagraph ASPIICS (Association of Spacecraft for Polarimetric Imaging Investigation of the Corona of the Sun). ASPIICS is developed and produced in cooperation of twenty partners from seven countries. It is a part of the ESA's PROBA-3 mission, which includes a formation flight of a pair of satellites at orbit. Coronagraph itself consists of three objectives, where the last one is composed by one objective tube for each lens plus holder and Lyot stop. To achieve high accuracy of mounting of the individual lenses, it was necessary to achieve tight geometric and dimensional tolerances for manufacturing of the objectives barrels. In order to minimize the stress and to prevent the displacement of the lens from ideal position during a temperature change on orbit, an athermal solution was proposed. This is achieved by inserting a Teflon ring of a suitable thickness between the lens surface, objective barrel and the spring washer with a precisely defined contact force. It was necessary to find a suitable technological process of manufacturing, because of the specific behavior of PTFE during turning and complex design of other parts. All parameters of mounting system were repeatedly verified by a thermomechanical analysis in FEM software, based on tests of real parts.

The presented paper aims to theoretically analyze the possibilities, advantages and drawbacks of standard methods used for the assessment of optical surface defects (the so-called Scratch and Dig analysis). Based on the acquired knowledge, we design and apply a process of SaD analysis suitable for the evaluation of optical surfaces of mirrors of the space coronagraph Metis, whose manufacturing was successfully implemented within the Centre Toptec in the past period.

We report on a design of an interferometric position measuring system for control of a sample stage in an e-beam writer with reproducibility of the position on nanometer level and resolution below nanometer. We introduced differential configuration of the interferometer where the position is measured with respect to a central reference point to eliminate deformations caused by thermal and pressure effects on the vacuum chamber. The reference is here the electron gun of the writer. The interferometer is designed to operate at infrared, telecommunication wavelength due to the risk of interference of stray light with sensitive photodetectors in the chamber. The laser source is here a narrow-linewidth DFB laser diode with electronics of our own design offering precision and stability of temperature and current, low-noise, protection from rf interference, and high-frequency modulation. Detection of the interferometric signal relies on a novel derivative technique utilizing hf frequency modulation and phase-sensitive detection.

Fourier-transform phase-shifting interferometry brings the possibility of a very precise measurement of refractive-index variation in a material. In a four surface cavity six first order interferograms are observed. In the standard way an interference between waves reflected from a front and a rear surface of a sample is used to obtain refractive-index homogeneity. But another three interferograms contain information about inner inhomogeneity and can be used for its calculation as well. In this paper all four calculation methods are presented and compared. The measurements and simulations show, the methods give us globally similar outputs. However due to calculation from different interferograms every result is affected by different undesirable effects. This difference can be used for suppression of the effects and thus to refine the results.

The paper present principles and derivation of the iterative method for solving the eikonal equation. The eikonal equation, which defines the relationship between the phase of the optical wave Φ(r) and the refractive index n(r), i.e. |grad Φ(r)|² = n²(r), represents the fundamental equation in geometrical optics. It describes the evolution of the wavefront, which is given by the equation Φ (r) = C, of the electromagnetic wave in the limit of infinite frequency or zero wavelength. The eikonal equation is the nonlinear partial differential equation (PDE) of the first order. This classification makes the eikonal equation of rather diffcult to solve, both analytically and numerically. Several algorithms have been developed to solve the eikonal equation: Dijkstra's algorithm, fast marching method, fast sweeping method, label-correcting methods, etc. Major disadvantage of these methods is that their convergence puts rather high requirements on the density of the computing grid. It is known that finite element method (FEM) offers much more memory and time efficient approach to solve PDEs. Unfortunately, FEM cannot be applied to solve eikonal equation directly due to its first order. In order to provide the fast and memory efficient solution of the eikonal equation, it is suggested to solve a generalized version of the eikonal equation, which is of the second order and which can be solved using FEM. Then, iterative procedure for computing the corrections of the obtained numerical solution is developed. It is shown that the computed series converges to the solution of the original eikonal equation.

Laser welding is a modern, widely used but still not really common method of welding. With increasing demands on the quality of the welds, it is usual to apply automated machine welding and with on-line monitoring of the welding process. The resulting quality of the weld is largely affected by the behavior of keyhole. However, its direct observation during the welding process is practically impossible and it is necessary to use indirect methods. At ISI we have developed optical methods of monitoring the process. Most advanced is an analysis of radiation of laser-induced plasma plume forming in the keyhole where changes in the frequency of the plasma bursts are monitored and evaluated using Fourier and autocorrelation analysis. Another solution, robust and suitable for industry, is based on the observation of the keyhole inlet opening through a coaxial camera mounted in the welding head and the subsequent image processing by computer vision methods. A high-speed camera is used to understand the dynamics of the plasma plume. Through optical spectroscopy of the plume, we can study the excitation of elements in a material. It is also beneficial to monitor the gas flow of shielding gas using schlieren method.

The paper presents analysis of the wavefront deformations of the optical waves transmitted through the ferroelectric single crystals with particular types of domain patterns by means of the numerical simulations. It is known that domain patterns influence the macroscopic properties of ferroelectric polydomain single crystals to a great extent. It is known that the domain spacing in ferroelectric single crystals can span the range from few tenths of nanometers to centimeters. Finally, it is known that measurements of the wavefront deformation can serve as input data for tomographic methods. In this paper, we perform exact numerical computations of the wavefront deformations of the optical wave passing through the ferroelectric domain patterns for different wavelengths. The considered simulations methods are based on solving the wave equation for the electromagnetic field. The computed numerical results are compared with simple analytical estimates. The key result of the paper is the benchmark of the limits for the three-dimensional observations of the ferroelectric domain patterns using digital holographic tomography.

This work presents detailed theoretical analysis of the effect of finite dimensions of an amplitude diffraction grating to the edge response function of the Talbot imaging. A diffraction of a plane wave is studied as well as a diffraction of a spherical one. The derived formulas can be used to refine the description of field propagation behind the amplitude diffraction grating; therefore, an analysis and an improvement of current applications, where the Talbot effect is used, can be realised.

This paper reports on phase retrieval method in non-nulling dual-wavelength interferometry. It uses synthetic phase as shape estimation for determination of fringe orders within every pixel. The fringe order map is subsequently used for unwrapping of phase measured at shorter wavelengths. It was experimentally shown that even for inaccurate synthetic phase, the computed phase for short wavelength is correct. The key point is in analysis of phase fields in spatial derivatives where the sensitivity to phase distortions is lower instead of analyzing the phase fields themselves.

We report on the discovery of new four variable stars in the Cassiopea constellation from the archive of the HALZ telescope, operated by the TOPTEC team at Horní Halže, near Klášterec nad Ohří, Czech Republic. The stars are catalogued as UCAC4 718-108144 (23h 04m 16.383s +53° 29’ 44.78”), UCAC4 725-101725 (23h 09m 27.87s +54° 51’ 23.27”), UCAC4 725-101699 (23h 09m 19.53s +54° 57’ 57.18”), UCAC4 722-105015 (23h 10m 42.4s +54° 14’ 33.33”). From the light curve, the stars should be a HADS – type variable (UCAC4 718-108144), an EW – type variable (UCAC4 725-101725), an EA - type variable (UCAC4 725-101699) and an ELL – type variable (UCAC4 722-105015). We registered these stars in the CzeV catalogue as new variable stars CzeV709, CzeV710, CzeV711 and CzeV715.

In our laboratory, we use for fabrication of volume phase diffraction gratings a photopolymer recording material Bayfol HX. It is an extremely effective recording material; a high value of the refractive index modulation is obtained already during a holographic exposure. The value of this refractive index modulation influences the diffraction properties (e.g. efficiency) of the recorded gratings and, in the case of transmission gratings, the growth of this modulation beyond the optimal value leads to an effect of so called overmodulation. This effect is, in the most cases, unwanted as it causes the decrease of the diffraction efficiency from its maximum value (practically close to 100%). The analysis whether the grating is over- or under- modulated is relatively difficult as the value of the refractive index modulation can’t be measured directly and it is evaluated from the measurement of the diffraction efficiency. However, the obtained value can be often incorrect due to the overmodulation effect. In this contribution, we would like to extend (to include any arbitrary slanted transmission gratings) and discuss a simple measurement method for the determination of the correct value of the refractive index modulation based on a multiple/two-wavelength measurement of a diffraction efficiency of transmission gratings. The theoretical idea of this method and also experimental results obtained on photopolymer Bayfol HX will be presented. From practical point of view, this approach help us mainly for correct adjustment of exposure parameters to reach efficient gratings.

The 8-inch Clark objective lens of the Astronomical Institute of the Czech Academy of Sciences is probably the oldest doublet used for professional astronomical observation in the Czech Republic. Its optical imaging performance has become legendary among several generations of professional astronomers. The lens was manufactured by Alvan Clark in Cambridge, Massachusetts at the end of the 1850s. The 8-inch refractor functioned as the main telescope of the astronomical observatory in Ondřejov in the first half of the twentieth century. The objective has been cleaned and restored twice in the TOPTEC Centre in Turnov. We had the opportunity to measure the optical parameters of the doublet during its time in Turnov and we subsequently evaluated its residual aberrations. This paper is a record of the results of the optical simulations.

Pb(Zr,Ti)O3 (PZT) is a ferroelectric material interesting for its high dielectric constant and piezoelectric response. PZT thin films can be prepared by various methods, e.g. pulsed laser deposition, chemical vapor deposition, sol-gel and, most frequently, sputtering. Though the magnetron sputtering is used more frequently, PZT thin films can be prepared also by ion-beam sputtering (IBS). In this paper we study the deposition process of PZT thin films in our IBS system with a possibility of ion-beam assisted deposition (IBAD), which has the advantage that more energy can be added to the growing layer. We show how in our system the resulting layers, mainly their quality, the Pb content, which is important for the creation of the perovskite crystal structure, and the resulting crystal structure are influenced by the oxygen flux during the deposition for the samples grown on the silicon substrate with and without an intermediate Ti seeding layer.

The paper describes an achromatic Steinhal type doublet that employs an aspherical surface to allow wide angle imaging. A design criteria, optimization techniques and tolerancing of the doublet are described. Further a manufacturing process of the system and achieved optical performance measurement is discussed. Benefits of the wide angle imaging doublet are recently planned to be used in automotive industry application, namely for optimizing of head-light performance and their final evaluation. The final device is planned to be part of the production line.

A digital holographic interferometry (DHI) for 3D measurement of temperature distributions in moving fluid is presented in this paper. The measurement uses digital holographic setup for measurement of a flow of fluid propagated through an orifice and tomographic approach for 3D reconstruction of the flow. The periodic character of the flow and synchronization between the digital camera and external trigger driving the phenomenon allows us to measure phenomena with much higher frequency when compared to frame rate of the digital camera. Furthermore one can capture a large number of the flow projections from different viewing directions which are later used for 3D tomographic reconstruction of the whole temperature field of the flow. The measurement results are verified and compared with hot wire method (CTA) in the paper.

Thin films of silicon dioxide (SiO₂) and titanium dioxide (TiO₂) for application in precision optics prepared via the solgel route are being investigated in this paper. The sol-gel process presents a low cost approach, which is capable of tailoring thin films of various materials in optical grade quality. Both SiO₂ and TiO₂ are materials well known for their application in the field of anti-reflective and also highly reflective optical coatings. For precision optics purposes, thickness control and high quality of such coatings are of utmost importance. In this work, thin films were deposited on microscope glass slides substrates using the dip-coating technique from a solution based on alkoxide precursors of tetraethyl orthosilicate (TEOS) and titanium isopropoxide (TIP) for SiO₂ and TiO₂, respectively. As-deposited films were studied using spectroscopic ellipsometry to determine their thickness and refractive index. Using a semi-empirical equation, a relationship between the coating speed and the heat-treated film thickness was described for both SiO₂ and TiO₂ thin films. This allows us to control the final heat-treated thin film thickness by simply adjusting the coating speed. Furthermore, films’ surface was studied using the white-light interferometry. As-prepared films exhibited low surface roughness with the area roughness parameter Sq being on average of 0.799 nm and 0.33 nm for SiO₂ and TiO₂, respectively.

The freeform and aspheric measurement in the industry is rather cumbersome. This situation led us to the decision to start the development of the metrology tool offering the measurement of grinded (diffusive) and polished (specularly reflecting) surfaces with arbitrary geometries and with the necessary fiducials. We proposed digital multiwavelength multidirectional holographic contouring with phase shifting. Recently we redesigned our system heavily e.g we use 16 independent illumination directions, we use new PSI algorithm, etc. The factor strongly influencing the method precision is the sensitivity vector field knowledge over the whole measured area. We proposed the method of the sensitivity vector map retrieval based on controlled movement and recording of the measured part with the data evaluation. The proposed method has been tested recently. The method fundamentals, experimental setup and the results are presented in this paper.

In order to measure an optical lens surface shape using optical interference with sufficient accuracy, it is usually necessary divide area into sub-apertures and then captures each sector separately. When the data are acquired, it is necessary to merge elements together for further analysis. This paper is primary about stitching sub-apertures on spherical and aspherical optical lens. The main content of this paper is mostly the description of a stitching procedure and troubleshooting during process. The paper for example contains a description how sub-apertures tilt was compensated and how sub-apertures rotation was solved. Another topic in this paper is dealing with final adjustment during stitching. The paper contains description for used algorithms. For example an algorithm for finding a sub-aperture centre and algorithm for overlap deviation evaluation are included in this paper. Very useful part in this paper is the description of used computational complexity optimisation methods. And finally real measured and processed data are presented.