This PDF file contains the front matter associated with SPIE Proceedings Volume 10692, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Modern electro-optical systems often include several channels for imaging at different bands. These systems are capped with a window assembly in which the optical windows are cemented to a frame using dedicated adhesives intended to seal the system’s internal optics from the outside environment. Such window assemblies may include several optical windows made of different materials, depending on the necessary spectral bands, and are usually very expensive. Occasionally, these windows, become damaged due to exposure to severe environments, and require replacement. In such a case, there is a need for a detachment process to remove and replace only the defective part without damaging the rest of the windows or the metal frame. In this work, we have developed a dedicated tool which enables cost-effective and selective detachment of only the defective parts without any damage to the rest of the window assembly. The detachment process is based on a 3-axis hotwire automated system that was inspired by the foam cutting industry. An electrical current is passed through a hotwire which is then used to selectively decompose the adhesive along the bond line. Parameters such as wire voltage, wire tension, and velocity were selected to yield the best performance, namely, quick and safe removal of the part. The flexibility of the system’s design allows for detaching windows of different geometries, materials, and sizes.

Thanks to their size and weight reduction and error correction potential, aspheric designs are seeing an industry-wide adoption. This not only increases demand for precise fabrication processes, but also fast and flexible metrology solutions for aspheric lenses. While many systems support measuring the surface topography, the process is limited to a specific design or based on a time-consuming scanning process. Centration measurement with such systems requires additional probes or the inclusion of external reference surfaces in the measurement process. In this paper, we describe how our automated lens testing system AspheroCheck UP is used for centration measurement and quality inspection of aspheres. It is based on the well-established AspheroCheck principle. The paraxial centering errors of both optical surfaces are measured in reflection using a focusing autocollimator. This centration measurement is combined with a fully motorized, non-contact distance sensor that measures the aspheric surface run-out at a single or at multiple locations along the surface. The sensor can also be used to measure various surface shape errors, outer diameter, flange and/or interlock surfaces and even double-aspheric lenses, enabling inspection of both inner and outer centration. A five-axis motorized table enables the automatic alignment of the optical axis of the sample to the rotation axis. This significantly reduces setup time and allows for fully automatic testing without user interaction, ensuring both high measurement accuracy and high repeatability independent of the operator. In addition to supporting standard polynomial surfaces, the system supports most other rotationally symmetric surface types, including Fresnel and diffractive surfaces.

The most important properties of optical glass types are transmission and dispersion. All other properties are second priority. Sometimes however, such glasses might have to endure high mechanical loads. Examples are with cameras subject to strong accelerations such as rocket launches loads or thermal stresses induced by temperature changes. Optical glasses also find use as windows with pressure loads. In such cases the question arises, which loads are allowable to prevent breakage and how can the strength of given optical elements be increased. In the last ten years considerable progress could be achieved in reliably predicting lifetimes of structures made from the glass ceramic ZERODUR. This work will show the transfer of the knowledge gained to optical glasses. The breakage stress threshold observed with ZERODUR exists also with optical glasses. We will show its usage for assessing short time loads and long-time loads taking into account the fatigue effect. The article will provide all available strength data and discuss how to estimate data for glass types without existing measurement results. For the lead flint glass types there is a good correlation of the breakage stress threshold with their lead content allowing predicting threshold values for all glass types in this glass type family.

Micro-optical array projectors are discussed as replacement for structured illumination in applications with critical space requirements. The concept bases on the fly’s eye condenser principle and a well-defined buried array of micro-dia. Their optical performance benefits from etendue conservation and the large depth of field of applied short focal lenses. As an established technique to generate microlens profiles, thermal reflow of binary patterned photoresist is known for more than three decades. This approach leads to lens arrays with filling factors up to ~90% when used in hexagonal arrangement. Further increment requires direct writing methods such as grayscale lithography. Recently a LED based projection stepper-like lithography system became competitive, because it allows structure depths beyond 50 microns. It utilizes an LCoS micro-imager as variable 8-bit reticle and a high dynamic dosage controlled illumination. This paper represents the evaluation of the technique for the generation of refractive lens profiles by means of metrology and optical performance of micro-optical array projectors. Micro-array projectors based on circular lenslets will be compared, followed by the analysis of closely packed square-shaped lenslets. The aim is to understand the impact of lens shape deviation, conical constant or statistical distribution of lens properties like sag height, radius of curvature on the projection. A correlation of imperfections and quality loss due to scattering, aberrations, and mismatch of images in the overlay of different projectorlets will be given. The work concludes with an outlook on further developments in mastering micro-optical profiles for illumination application.

A new method for calibrating optical scanning profilometers is presented. Especially adapted to spherical and aspherical profile measurements, it shows an increase of accuracy bigger than one order of magnitude for radius of curvature measurements. Calibration of vertical scaling is obtained with a reduction of its uncertainty by a factor larger than 2, which also demonstrates the advantage of this method for any surface measurements. Using commercially available reference balls, this method is easily implementable.

The paper is aimed at the development of multi-valued holographic plane angle measure, so called, holographic prism. The holographic prism serves as a base of a device for calibration of equipment (swinging platforms) for navigation apparatus test on influence of rolling. The holographic prism is a small specimen of photosensitive material which a system of superimposed holographic gratings is written in, and a laser used for the gratings readout. Under the influence of the laser, a fan of diffracted beams is induced in the specimen. Consisting of the test device, the holographic prism is mounted on the platform, and while as it swings the fan moves along a photo-detector, for instance, CCD-sensor. First, fluorite was selected as a photosensitive material for the holographic prism. But it had several major drawbacks. Application of photothermo- refractive glass as the photo-sensitive material for the holographic prism manufacture permits to overcome these drawbacks. The hologram number is increased up to twenty-one. The fan proves to be very plane. The fan center is located in a domain which is of small size equal to some part of the specimen thickness (1-2 mm). The fan beams are energy-wise uniform, and every beam can be identified by using the fan in the test equipment. For instance, the beam can be coded, for its identification, by known angles between that beam and the adjacent ones. At last, the hologram recording in photothermo- refractive glass is much easier than that in fluorite.

The World Space Observatory--Ultraviolet (WSO--UV) is a Russian-Spanish space mission born as a response to the growing up demand for UV facilities by the astronomical community. It is the only 2-meter class on-orbit telescope in the after--HST epoch fully devoted to UV observations in the spectral domain of 115-310 nm. This paper provides an information on instrumentation upgdate and the project status in 2018.

In dec 2015, during COP21, France has initiated the development of the MicroCarb satellite dedicated to better understand the carbon cycle within our atmosphere and to predict its evolution. CNES selected Airbus Defense and Space for the development of the instrument and Safran Reosc has been selected for the optical polishing of the key optical components of this innovative compact spectrometer, the first in EU of its class entirely based on precision freeform optics. The benefits of freeform optics will be highlighted before introducing to the MicroCarb satellite and instrument optical design. Our joint design efforts with Airbus Defense and Space towards ‘feasible’ optics will be presented with the latest technology development at Safran Reosc on freeform optics polishing technology.

EUCLID is an optical/near-infrared survey mission to be launched towards the L2 Lagrange point. It will aim at studying the dark universe and providing a better understanding of the origin of the accelerating expansion of the universe. Through the use of cosmological sounding, it will investigate the nature of dark energy, dark matter and gravity by tracking their observational signatures on the geometry of the universe and on the cosmic history of large structures formation. The EUCLID PayLoad Module (PLM) consists of a 1.2 m-class telescope and will accommodate two instruments. As a subcontractor of AIRBUS Defence and Space, AMOS is responsible for the manufacturing of all the silicon carbide mirrors of EUCLID PLM except for the primary mirror. In addition, AMOS also produces the 1.3 m test collimator that is used for the on-ground validation of the optical performances of the payload module under operational thermal vacuum conditions. The 1.3m collimator is designed, manufactured, assembled and tested by AMOS. It is based on a Ritchey-Chretien optical configuration, with a f/2 primary mirror and a hyperbolic secondary mirror. The mirrors are made of ZERODUR® and polished by AMOS. The high performance of EUCLID PLM calls for not less demanding requirements for the test collimator, in terms of image quality, thermal stability, line of sight stability under micro-vibration, etc. Here after are presented at first the design and the strategies elaborated to cope with the stringent requirements. Then, the manufacturing and metrology of the mirrors are reported. Finally, the Assembly, Integration and Verification by test (AIV) are discussed.

Additive manufacturing enables enhanced designs for metal mirrors and housings of optical systems like telescopes. Internal lightweight structures are used for the mirror modules to reduce the weight of the system while keeping the mechanical stability. Internal structures can be produced by selective laser melting, which cannot be realized by conventional machining. Using an aluminum silicon alloy, the thermal mismatch of the mirror base body to the necessary polishing layer is minimized. Resulting thermal induced deformations are greatly reduced. The additive manufacturing of a mirror module with two optical surfaces is described in detail. Using a adapted process chain for the application in the visible range, first results of the additive manufacturing as well as subsequent machining steps like diamond turning of the optical surfaces are presented.

The Spectral Separation Assembly (SSA) is a key component of the Flexible Combined Imager (FCI), an instrument that will be onboard Meteosat Third Generation (MTG). It splits the input beam coming from the telescope into five spectral groups, for a total of 16 channels, from 0.4 to 13.3 μm. It comprises a set of four dichroics separators followed by four collimating optics for the infrared spectral groups, which feed the cold imaging optics. To assess the optical performances, a specific multi-wavelength infrared test bench has been designed. The wavefront error can be measured for each channel of each spectral group. Other parameters can also be measured, namely pupil centering, line of sight, pupil diameter and pupil aberrations. This paper will present this test bench and the solutions developed to enable these measurements on a very large spectral range.

Defects in multilayer coatings significantly increase scattering loss and degrade the performance of the advanced laser systems like gravitational wave detection, laser gyroscope and ultraviolet laser, etc. The quantitative description of the defect-induced scattering in multilayer coatings was rarely addressed. In this work, the scattering characteristics of the nodular defects in Ta₂O₅/SiO₂ multilayer coatings for 1.064 μm wavelength was simulated using finite-difference time-domain method. First, the simulation process was given, several important steps that include structure modeling, far field calculation and far field to angular resolved scattering were presented. The scattering distributions of the nodular defects are similar to Airy diffraction pattern that is from a circular hole. The roughness-induced scattering from the coatings was calculated using first-order perturbation theory. The characteristics of the defect-induced scattering is significantly different from the roughness-induced scattering. The total scattering loss is approximately three orders of magnitude stronger than the roughness-induced scattering.

The accurate simulation of straylight is essential for the verification of the contrast requirements in optical instruments. In a spectrometer, the scattering from reflective gratings is hardly understood and difficult to characterize while contributing significantly to the overall system straylight and reduction of the spectrometer contrast. In this article we present an experimental setup for, and measurement results from, the characterization of the bidirectional scattering distribution function (BSDF) of a grating in the scope of the FLORIS project of the ESA FLEX Mission. The grating is an Engineering Model and will be subject to further optimization. Measurement of the BSDF showed approximately a Harvey-Shack profile parallel to the grating grooves, consistent with a dominant contribution from roughness scatter and minor distinctive features. Moreover, we observed distinct straylight peaks out of the diffraction plane, which are called “satellites”. The main challenges in the measurement of grating BSDFs arise from the near angle limit, the determination of the instrument signature and the selection of the appropriate sampling (2D or 3D). Theoretical analysis has been performed to investigate the influence of, and limitations introduced by, the measurement setup combined with the convex curvature of the grating. The next step is to introduce these measured BSDFs into straylight simulation. We have done that by fitting appropriate functions to the measured BSDF and defining them in the optical analysis software ASAP as a user-defined BSDF.

The sensing performance of spectroscopic systems can be enhanced by improving their optical core-element: the optical grating. in particular for imaging spectrometers - especially Hyper-Spectral Imagers - beside the polarization sensitivity and efficiency the imaging quality of the diffraction grating is an important parameter. Optical elements within the spectrometer are manufactured while aiming on lowest wave front aberrations. Thus, least imaging aberration quality of the grating is required not to limit the overall imaging quality of the instrument. Different types of spectrometers (Offner, Czerny Turner) lead to different requirements for the grating surface figure. Beside wavefront aberrations the straylight of gratings will impact the optical performance of spectrometers too. Both parameters are crucially influenced by the manufacturing processes. During the manufacturing process of the grating substrate, a sequence of polishing steps can be applied in order to minimize the wavefront aberrations and roughness. Chemical assisted polishing in combination with classical techniques lead to least surface roughness. A good practice for the manufacturing of aspheres and freeform substrates is the generation of an initial figure close to the final shape only by a classical process, followed by a careful applied aspherization. The imaging performance (wavefront and straylight) of the grating is also optimized due to the recording setup of the holography - including all employed optics for the wave forming. Holographically manufactured gratings with adapted wave forming functions are used for transmission or reflection gratings on different types of substrates like prisms, convex and concave spherical and aspherical surface shapes, up to free-form elements. Numerous spectrometer setups (e.g. Offner, Rowland circle, Czerny-Turner system layout) work on the optical design principles of reflection gratings. All those manufactured gratings can be coated with adapted coatings to support their reflection or transmission operation. The present approach can be applied to manufacture high quality reflection gratings for the EUV to the IR. In this paper we report our results on designing and manufacturing high quality gratings based on holographic processes in order to enable diffraction limited complex spectrometric setups over certain wavelength ranges. Most beneficial is an optimization of the grating during spectrometer design phase while regarding the manufacturing as well. However, the initial optical design approach will show that gratings can be tailored to the specific requirements of the spectrometer (in order to enhance the imaging quality). The enhancement of the optical performance may lead to a specific wavefront shape after the grating element. this special capability for aberration reduction can be defined to the grating during the holographic process. In general, holography enables to manufacture gratings with a specific and adapted wavefront error compensation functions. Beside the results of low aberration gratings the results on straylight measurements will be presented. Recent results and optimization will be shown.

In recent years, the scattering properties of optical gratings became of high interest. In particular, the effect of line edge roughness (LER) in lamellar diffraction gratings was identified to be a potential source of stray light. In this contribution the LER-induced scattering spectrum of such gratings is investigated. The straight-forward method to calculate the angle resolved scattering (ARS) is offered by two-dimensional simulation tools, e.g. the rigorous coupled wave analysis (RCWA). Unfortunately, this approach suffers from computation times that typically lie in the range of several days. As a simplification, we apply a novel one-dimensional rigorous approach1 that permits the prediction of ARS along the dispersion direction of the grating within a feasible computation time. As the 1D-model only accounts for the LER-parameter σ and neglects the correlation length ξ and the roughness exponent α, analytical considerations must be employed in order to adapt the 1D-simulation results to the 2D-reality.1 The model is verified by comparison to the 2D-model and ARS-measurements of E-beam exposed gratings with artificially induced (and strongly determined) LER. Based on the derived 1D-model, the effects of different parameters on the straylight performance of a high performance spectrometer grating is investigated. As a result we find that not only the roughness parameters but also the grating geometry has a significant effect especially on the spatial distribution of the scattered light. In other words, the strength of the scattered light next to the (spectrometric) useful diffraction order can be controlled by the grating geometry, too. Hence, the presented algorithm might be a useful tool for designing gratings with strong straylight specifications.

Metal mirrors have different advantages in comparison to mirrors made of glassy ceramics and glass elements as they are inexpensive, easy to manufacture and it is possible to integrate reference structures directly into the mirror material. During the last years diamond turning manufacturing of multi mirror freeform substrates became state of the art to reduce the alignment and integration effort of freeform mirror systems. The article gives an overview over the process chain, data analysis, and results from a mirror system for the visual spectral band and provides some theoretical insights necessary for achieving appropriate surface form and roughness values.

Freeform optical shapes or optical surfaces that are designed with non-symmetric features are gaining popularity with lens designers and optical system integrators. Manufacturing and testing details will be discussed for freeforms as well as current manufacturing tolerancing limits. This paper will address challenges that have been encountered in the manufacturing, testing, and handling of freeforms as their size expands up to and beyond 500 mm, and provide future work that will address each challenge.

Ion beam figuring with low-energy ion beam tools is a widely used finishing technique for most precise optical devices 1-3. For the machining of strongly curved surfaces as well as the correction of low-to-mid spatial frequency figure errors the usage of a high performance ion beam source with low tool width is mandatory. For that reason two different concepts of ion beam generation with high ion current density and narrow beam width are discussed: 1) A concave ion beam extraction grid system is used for aperture-less constriction of ion beams in the low millimeter range. An oxygen ion beam with a full-width at half maximum (FWHM) of 4.0mm with an ion current density of 29.8mA=cm² was achieved. 2) For even smaller ion beams a conic aperture design with a sub-millimeter sized exit opening has been tested. A nitrogen ion beam with a FWHM down to 0.62mm with an ion current density of 4.6mA=cm² was obtained.

Aluminum (pure or alloy) mirrors attract increasing interest, having Young’s Modulus and density similar to glasses. Advantage of high diffusivity offsets disadvantage of high thermal expansion coefficient and means that the mirror reaches thermal equilibrium rapidly. High ductility supports extreme light-weighting and complex machining, including fluid-cooling channels in high-energy applications, and integral interface components. Aluminum mirrors are also tolerant to vibrations and shock loads. The material is amenable to single point diamond turning (SPDT) and does not require optical coating. However, SPDT tends to produce mid-spatial frequency artefacts, which are difficult to remove, especially for aspheres and free-forms. These introduce diffraction effects and compromise stray light performance. In our previous research, we have demonstrated the potential of industrial robots to automate manual interventions with CNC polishing machines, and to provide surface-processing capabilities in their own right. We have also presented research concerning the mismatch between rigid and semi-rigid tools (including non-Newtonian tools), and aspheric surfaces. In this paper, we report on polishing of spherical and aspheric aluminum mirrors using an industrial robot. This includes tool-design, tool-path generation, texture control and removal of the mid-spatial frequency artefacts. We have investigated removal-rates and textures achieved, using different specialized slurries, polishing pads and special tool-paths. An effective process has been established, achieving Sa of 5nm on a 400mm square witness sample and a 490mm elliptical off-axis parabolic mirror.

Compared to spherical and aspherical lenses freeform shapes are much more challenging for the measurement required in the production process. A lot of metrology systems available for measuring spheres and aspheres are not capable of measuring freeforms. In addition lenses with a freeform surface may also contain reference elements whose position has to be determined. However, there are a few types of instruments which can in principle perform measurements of freeforms. Challenges of measuring freeforms are discussed and different types of potential measuring instruments and their capabilities are presented. This is demonstrated providing measuring results from different samples measured with different instruments.

We design a TMA telescope for nanosat uncooled IR applications and manufacture one of its mirror using a ceramic 3D printing process. The TMA design serves as pretext to obtaining a very fast (N = 0.63) mirror to manufacture, we nonetheless gloss over a typical optical design workflow, with optical optimization, tolerancing and stray-light analysis. The metrology of the manufactured mirror will involve deflectometry, for which we give a bibliography. We manufactured one TMA mirror extracted from our design using laser stereolithography (SLA) 3D printing process for ceramic parts.

Recently, freeform surfaces have been widely used in various optical systems because of their high flexibility and ability to correct aberrations when off-axis optical components are considered. Among freeform optics there are the head-up displays (HUDs) for vehicles, HUDs are increasingly used in new vehicles as they keep the driver’s head up and eyes focused on the road for the sake of improved safety. Fora compact size in the limited space of the vehicle, an HUD is typically an off-axis mirror system (including the windshield). The freeform mirror is not only employed to correct the off-axis aberrations caused by the windshield but also is used to provide an optical power for system magnification. This paper focuses on the design, fabrication, and measurement of a freeform mirror developed for a vehicle HUD system. We herewith report the design of the freeform surface including extended its polynomials description and its optimization. Using an ultra-high precision manufacturing and metrology strategy that is based on the use of a multi-axis machining center and advanced nano-metric profiler, the form error of the freeform mirror was precisely controlled according to system requirement. The fabricating method was realized on a machine equipped with a servo tool servo (STS) a and the combination of CXZ coordinates was programmed,. Finally, the freeform surface is fabricated and measured experimentally by ultrahigh accurate 3D profilometer.

Since two decades Safran Reosc is developing best technique to offer polishing services of Silicon Carbide to the optical community, especially for space applications. Today we want to share with the community our efforts along various actions of progress for improving the quality of our work and our industrial efficiency in the production of SiC optical components which are key enabler of many demanding optical instruments.

Ductile mode machining is usually applied for the optical finishing operation of e.g. tungsten carbide molds to be used for precision glass molding. In this paper, we report on a process analysis of ductile mode machining analyzing the influences of critical process parameters on the level of surface roughness being generated for tungsten carbide. To that aim, a recently developed method for process optimization in optics fabrication, the three wagons method, was applied identifying critical process parameters determining the eventual level of surface roughness within the ductile process window of UPM machining. Based on the experimental data collected, a new formula was developed enabling the prediction of the level of surface roughness being generated by ductile machining. Applying this formula, an optimized set of critical process parameter values has been determined predicting a minimum level of surface roughness on tungsten carbide (CTN01L) by ductile mode material removal of about 1 nm rms which has been proven in experiment. The developed formula enables a better predictability of level of surface roughness within the process window of ductile mode machining.

Ductile mode grinding is a finishing process usually being applied to generate molds in brittle materials (e.g. tungsten carbide) to be used for precision glass molding (PGM). To that aim, ultra-precision machineries (UPM) are applied controlling depth of cut not to exceed a critical value, hcu,crit (e.g. 160 nm for tungsten carbide). Recent process analyses of the ductile mode grinding process of brittle materials have demonstrated that the critical indentation depth hcu,crit, that determines the transition from brittle mode to ductile mode removal, can significantly be shifted to higher values by adjusting process parameters such as the type of coolant and its pH value: e.g. for tungsten carbide up to 1600 nm and for BK7 glass up to 350 nm depth [1] Consequently, this paper reports on two experimental feasibility studies to extend the process window of ductile mode grinding of brittle materials. Applying ductile process parameter sets featuring values of the critical depth of cut larger than 1 micron depth two processes were experimentally analyzed that are up to now not applicable in industrial production environments: a) single point diamond turning (SPDT) of BK7 glass applying UPM machineries and b) ductile grinding of tungsten carbide molds applying standard CNC grinding machines featuring lower tool positioning accuracies than UPM. Experimental data of both tests will be presented demonstrating that by controlling and adjusting ductile process parameters only, it is possible to extend its process window into regimes that are today not yet machinable.

Ductile mode grinding is usually applied for finishing of e.g. tungsten carbide molds used for precision glass molding (PGM) by controlling depth of cut on feed controlled machines. Bifano et all. demonstrated the possibility to apply this mechanism while machining hard and brittle materials by the use of ultra-precision machines (UPM). Based on experimental investigations a formula for the transition from brittle to ductile cutting mechanism, also known as the critical depth of cut hcu,crit, relating the material specific properties Young’s-Modulus E, material hardness H and fracture toughness KC was developed [1] and is widely used for setting up UPM machines ever since. However, the influence of cutting conditions, like tool or process characteristics, are neglected leading to discrepancies of the value of hcu,crit between the prediction and the actual machining results of up to 200%. Furthermore, previous investigations have shown that hcu,crit strongly depends on coolant fluid characteristics as well as on the compressive stress applied into the cutting zone by the use of tools with e.g. negative rank angles [2]. In this paper, we report on a ductile grinding process analysis applying a recently developed method for process optimization in optics fabrication [3]. Following that trail, critical process parameters have been identified determining the process window of feed controlled ductile grinding applied on State-of-the-Art UPM machineries. The influences of the critical process parameters on the critical depth of cut hcu,crit have been tested experimentally using an ultra-precise SPDT machine. Among others, four critical process parameters could be identified determining the transition between brittle and ductile mode grinding: the critical depth of cut depends substantially on (a) the type of coolant used, (b) the pH value of the coolant, (c) the tool tip radius of the applied diamond and (d) whether ultrasonic assistance (US) is being switched on or off. Depending on the applied set of process parameters and for the experimental data collected, maximum ductile mode material removal rates could be achieved with hcu,crit, max = 1600 nm. That way, a new formula was developed, which allows the prediction of the critical depth of cut depending on critical process parameters, a.o. tool parameters and cutting fluid characteristics, while machining e.g. binderless nanocrystalline tungsten carbide or BK7 glass. This formula was set up based on fundamental ruling test results and is one step towards extending Bifanos formula taking the influences of critical process parameters into account.

Grinding processes offer a huge range of parameters affecting quality and quantity of the optical elements being produced. Systematic optimization can reveal unexploited potential even in already "stable and efficient" processes. In this paper we describe a method for optimizing CNC grinding processes under industrial conditions by applying a Preston-based approach. As already reported by Mr. Preston [1], for load controlled grinding processes, the workpiece material removal rate (MRR) is proportional to the applied tool pressure (P) multiple the applied relative speed between tool and workpiece (vr): MRR = c*P*vr. Consequently, while maintaining the relative speed (vr = const), there is a linear dependency of MRR on the applied pressure P existing within the process window. The method reported in this paper uses the inverse conclusion that outside of the process window, the linear dependency of MRR on P is not valid any more. This effect is being used to determine the process window of feed controlled CNC grinding processes, since spindles and slides of modern feed controlled CNC grinding machines have finite stiffness values. Therefore, we can apply a load controlled approach to determine the process window of feed controlled grinding processes. To that aim, a dynamometer was mounted onto a fixed abrasive, feed controlled, standard optics CNC grinding machine, monitoring tool pressure in situ and in process for different values of CNC machining parameter sets such as tool rotation, workpiece rotation and infeed speed etc. Experimental data will be presented determining the process window of various CNC grinding processes demonstrating that applying grinding process parameter sets within the process window boundaries guarantee a stable and predictable production with high yield values.

In this work, the topography of human corneas is evaluated with a conical corneal topographer based on the null-screen method. Geometrical parameters such as the radius of curvature and the conic constant, are obtained. Additionally, elevation, sagittal curvatures and meridional curvature maps can be calculated with the proposed method. Here, it is assumed that the shape of the cornea surface is an aspherical surface. To validate our proposal, we compare the results with those obtained by a commercial corneal topographer.

Optoelectronic devices based on array image sensors become more popular every year. They are used in science applications, as the machine vision systems and used by customers all over the world for image recording purpose. The quality of the image received by any optoelectronic system depends on several factors and such characteristic as its resolution turns out to be one of the most important. There are several ways to describe the optoelectronic system resolution. One of the most widespread is modulation transfer function. The modulation transfer function measurements could be fulfilled with the help of a method of summation over different frequencies harmonic functions. This method is accurate in the range of Nyquist frequency and closely meets the definition of the modulation transfer function as the harmonic functions are used. It also allows to input necessary frequencies by adding the sinusoid of corresponding frequency to the initial function. In this paper we describe the experiment of optoelectronic system modulation transfer function measurement using the above mentioned method.

Control stray light is very important in space industry. Indeed, it is one of the main factors in the decreasing of the signal-to-noise and the contrast. Stray light is generally caused by scattered light and ghost images. The Bidirectional Scatter Distribution function (BSDF) measurements allow the quantification of the scattered light by an optical element and becomes an important data to take into consideration when designing telescopes. Standard BSDF measurement goniophotometers often have a resolution of about 0.1° and are mainly working in or close to the visible spectrum. This resolution is far too loose to characterize ultra-polished surfaces. Besides, wavelength range of BSDF measurements for space projects needs to be done far from visible range. How can we measure BSDF of ultra-polished surfaces and diffraction gratings in the UV and IR range with high resolution? We worked on developing a new goniophometer bench in order to be able to characterize scattering of ultra-polished surfaces and diffraction gratings used in everyday space applications. This ten meters long bench was developed using a collimated beam approach as opposed to goniophotometer using focused beam. Sources used for IR characterization were CO₂ (10.6μm) and Helium Neon (3.39μm) lasers. Regarding UV sources, a collimated and spatially filtered UV LED was used. The detection was ensure by a photomultiplier coupled with synchronous detection as well as a MCT InSb detector. The so-built BSDF measurement instrument allowed us to measure BSDF of ultra-polished surfaces as well as diffraction gratings with an angular resolution of 0.02° and a dynamic of 1013 in the visible range. In IR as well as in UV we manage to get 10⁹ with same angular resolution of 0.02°. The 1m arm and translation stages allows us to measure samples up to 200mm. Thanks to such a device allowing ultra-polished materials as well as diffraction gratings scattering characterization, it is possible to implement those BSDF measurements into simulation software and predict stray light issues. This is a big help for space industry engineers to apprehend stray light due to surface finishes and to delete those effects before the whole project is done. We are now thinking of possible improvement on our optical bench to try to get dynamic in IR and UV similar to what we have in visible range (e.g. 10¹³).

The article presents the basics of modeling the surface microstructure using a bidirectional reflectance distribution function. Presented new model based on selected elements of the Torrance-Sparrow model and the HTSG model. The combination of empirical and physical model has made it possible to reduce the computational cost, without lowering accuracy of estimated parameters of material microstructure. Analysis of the computational cost was performed for empirical models: Lambert, Phing, Torrance-Sparrow, Shlick-Phong and physical model: Ward, Shlick, HTSG, Lafortune. The results showed that the presented model requires 30% more computational cost compared to empirical models but compared to physical models, the computational cost was reduced by 2.5 times, while maintaining the same accuracy of estimated parameters. The next part presents the temperature influence on power output of photovoltaic panels. The analysis was made for silicon cells SRT-100, SRT-50 and the amorphous tandem MST-50.

We propose 3-step fabrication procedures for aspheric surface with larger departure. First step is to generate a specific aspheric surface with SSD depth under 10μm. Next step is to remove SSD and to keep the aspheric form by using Zeeko polisher with higher MRR pad. Final step is to figure and finish the aspheric surface by using QED MRF machine. In this study, we focus on 1st step to investigate the residual depth of SSD after grinding process on fused silica. The abrasion (Aa) or grindability is one of mechanical properties of glass material. The evaluation method of abrasion or grindability is different between the manufacturers. In this study, we apply the specific grinding parameters with #400 and #800 cylindrical diamond wheel on Tongtai GT-630 5-axes machine center. The ultrasonic assisted module is combined with BBT 40 tool arbor. The specifications of the ultrasonic unit are 15 - 45 kHz in frequency range, 0.2-2.5 μm in amplitude, and 1,000 Watt in power. The cross-grinding configuration is used in this study, due to its advantages of non-sensitive cutting direction in Z-axis, high cutting capability with large tools, and low cutting force for generating large convex aspheric surface. Before inspecting the SSD of the samples, wedge polishing would be applied on the ground surface for each sample. In general, the micro cracks of SSD aren’t observed easily by optical microscope due to the micro cracks were stuffed by abrasives of slurry and removed powders of glass. Thus, the mixture solution with hydrofluoric acid (HF) and hydrochloric acid (HCl) in water is used to etch ground surface. After etching, the micro cracks of SSD can be measured by Keyence VK-9700 confocal microscope. The depth of SSD is calculated by length of SSD and wedge angle of the plane.

This contribution deals with the problem of determination of basic parameters of unknown lenses, namely their radii of curvature, thicknesses and refractive indices of materials (e.g. optical glasses) from which these lenses are made. The aim of this work is to present and analyze a method for the determination of internal parameters of unknown lenses, namely index of refraction and Abbe number. The method is proposed to obtain these parameters and mathematical relationships are derived that allow us to determine the refractive index and Abbe number of lens material based on the measured radius values, the thickness and the position of the focal point or the focal length. It is also performed an uncertainty analysis of the proposed method.

Precise measurement of extremely small tilt angles is of immense importance in various scientific and technological applications. Interferometry has always been a tool of great importance in such applications. Most of the conventional interferometric techniques use a Michelson configuration and the problem with this interferometer is that it is extremely sensitive to environmental turbulances and vibrations. In our privious works, we had introduced a cyclic interferometer for the measurement of tilt angles which showed excellent stability against environmental turbulances and vibrations as well as twice the sensitivity. Also, with the introduction of multiple reflections, sensitivity as low as 5 micro radian had been achieved by us. To improve the sensitivity further, we had employed phase shifting techniques. The cyclic configuration being a same path interferometer, we used a polarizing phase shifting technique. For acieving this, we developed a new scheme of polarizing phase shifting techique which is rather simpler compared to those reported in the literature. With this we could precisely measure angles as low as 2 nano radians. However, in these measurements we found that the precise alignment of the quarter wave plate plays an important role in the visibility of the fringes which affects the accuracy of measurement. In this work, we numerically investigate the effect of the misalignment of the quarter wave plate on the visibility of the fringes and consequently on the accurcy of the measurement.

The Student Research Laboratory for Optical Engineering was founded in 2014 at the Dept. of Applied and Computer Optics in ITMO University. Students there work on various optical, design, lighting and technological projects and find like-minded team for creating of coworking-groups in the student laboratory. It is highly difficult to provide practicaloriented activity in the laboratory without the use of elementary optical elements, which are supposed to be components of educational projects and activities. The review of traditional approaches for production of optical elements showed that currently there are no technologies in the optical industry, capable of solving this problem. The produced optical components must meet following requirements: a). to be capable to visualize optical elements work principles; b). to be produced rapid and laborless; c). to be affordable for students. This paper presents results of the experimental work, the technological process and the obtained elements characteristics, which were produced in two different ways. The optical elements angles were measured by goniometer and compared with preset tolerances.

High resolution and large relative aperture have been urgent demands for the development of spectrometer. A design method of freeform was presented based on offner structure, The design of large relative aperture was realized by multi variables of freeform surface, the energy of system was doubled. The simulation was carried out by the methods. Spectrum of the system is 400~1000nm, the relative aperture is 1/2.4, the length of the slit is 20mm, and the number of spectral is 213. Based on the aberration theory, the system was optimized and the processing feasibility was analyzed. The analysis results show that the optical MTF of each wavelength is more than 0.7@42lp/mm, and the structure was compact. The system has the feasibility of processing and meets the needs of remote sensing.

In the present work we present a novel approach of the null-screen test for testing a Parabolic Trough Solar Collector (PTSC) that involves the usage of custom designed dynamic patterns projected on a LCD display, in a new off-axis disposition that allows for more consistent retrieval of information as well as the ability to extract larger amounts of data in each test. We present images depicting an ongoing test that show clearly the advantages of this method compared to earlier versions of the null-screen test for the same collector.

Today radio based wireless communication technologies offer limited performance, whereas optical wireless com- munication systems (OWC) propose potentially a high performant, scalable communication system conforming to real time conditions. However, current studies imply, that OWCs still lack the necessary performance and robustness level for most wireless applications in industrial production environments. In this approach several types of noises for free-space optical communication systems are empirically analysed in an accredited, exemplary industrial production environment. While the channel noise is usually modelled by the signal to noise ratio it is found that real environments cannot be approximated by the usual static additive white gaussian noise. In this approach the accumulated measurement data represents the spectrum variation of different locations and times relating to different types of noise sources. The implementation in a total channel model allows the optimization of OWC designs like the channel access scheme or the modulation type concerning performance and robustness. Furthermore an additional measurement setup is proposed, capable of measuring and classifying existing noise sources in order to serve the design of OWC systems in industrial production environments.