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The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is selected by ESA for the ENVISAT-mission, scheduled for launch in 1999. The instrument will measure the concentration of atmospheric trace gases in the earth atmosphere in a spectral region from 4.15-14.6 rim. MIPAS consists of scan mirrors, a telescope, a Michelson Interferometer, an optical reducer and a focal plane assembly. The optical reducer consists of a 2 concave and 1 convex mirror system. The focal plane assembly consists of a configuration of mirrors and dichroics, with which the spectral range is divided in 4 spectral bands. TNO Institute of Applied Physics has designed the optical/mechanical system and after manufacturing of the components has aligned the system with high accuracy. The design and alignment of this system is described.

This article will give an overview of all effects that determine the spectral features amplitude (SFA). The origin of spectral features is explained and methods are indicated that can be used to minimize the SFA. Spectral features are observed in the ratio between two spectra of sun calibration measurements. Mechanisms helping to reduce spectral features are spectral averaging, angular averaging, and temporal averaging. It will be shown what optical design choices can be made in order to benefit from these SFA reducing mechanisms. In the final chapter some insight in the modeling is given where four types of diffusers are compared. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

This paper presents the TNO share of the development of the HIFI Alignment Camera System (HACS), covering the opto-mechanical and thermal design. The HACS is an Optical Ground Support Equipment (OGSE) that is specifically developed to verify proper alignment of different modules of the HIFI instrument during on-ground thermal (vacuum) testing of the ESA Herschell spacecraft.

Spectral features are introduced by the diffuser that is used during on-board sun calibration. New findings are presented on how to reduce the size of these spectral features. Reduction can be obtained via optical design of the calibration unit, but also in creating a better diffuser. A novel diffuser design will be presented and its performance will be compared to standard diffusers like an Aluminum diffuser, a Spectralon diffuser, and the QVD (Quasi Volume Diffuser). For the in-house spectral features testing setup an improvement of about a factor of eight was obtained for the new diffuser type when compared to QVD. QVD in its turn is already better than an Aluminum diffuser by a factor of ten. Spectralon and QVD are found to be about equally good when measured in terms of spectral features reduction. The novel diffuser is referred to as SanDiff since it is a sandwich of QVD and PTFE material. For the SanDiff also the BSDF was measured and will be presented here. © 2009 SPIE.

We present a novel optical design tool that makes use of an evolutionary global optimization algorithm. The algorithm has several characteristics that make it well-suited for freeform optics design. With the design tool it is no longer necessary to make the distinction between paraxial degrees of freedom and degrees of freedom related to freeform surface description. The design process, which typically involves a multi-stage scheme consisting of finding an optimal paraxial starting layout, optimization, gradually including freeform degrees of freedom to yield an optimal nominal design, and finally a step in which the as-built design is optimized, is shortened because optimal paraxial starting point and optimal freeform shapes are combined to a single optimization step. Optionally, as-built performance can be included in this step as well. The design tool is applied to the design of a compact spectrometer.

We present the optical configuration of an imaging filter spectrometer, part of the European Space Agency Multi-Spectral Imager instrument, that will provide information on the clouds for a better understanding of Earth climate.

We show that in the lens design landscape saddle points exist that are closely related to local minima of simpler problems. On the basis of this new theoretical insight we develop a systematic and efficient saddlepoint method that uses a-priori knowledge for obtaining new local minima. In contrast with earlier saddle-point methods, the present method can create both positive and negative lenses. As an example, by successively using the method a good-quality local minimum is obtained from a poor-quality one. The method could also be applicable in other global optimization problems that satisfy the requirements discussed in this paper.

The fact that every spectrometer can sort light by wavelength at the speed of light is intriguing. The field of spectrometry is a long-existing and ever-changing one. The application areas extend from optical communication to possible extraterrestrial life detection, health monitoring, environmental monitoring and quite a long list of other topics. TNO has played a role in several of these areas, always using state of the art designs and components. Some of the recent developments are described, as well as a possible path for (near) future developments. Any spectrometer consists of a telescope, slit, collimator, disperser and an imager. Each of these functions is discussed using and even pushing progress in the manufacturing and design capabilities of the industry. The progress from a two-mirror spherical telescope for a pushbroom space-based daily global coverage spectroscopy instrument OMI to a two-mirror freeform telescope for TROPOMI is described, the design and manufacturing of supergratings showing very little straylight, freeform mirrors and the use of deliberately decentered lenses is shown. A near-future small-satellite system is shown that is being built and tested as this paper was written.

In the design of a large adaptive deformable membrane mirror, variable reluctance actuators are used. These consist of a closed magnetic circuit in which a strong permanent magnet provides a static magnetic force on a ferromagnetic core which is suspended in a membrane. By applying a current through the coil which is situated around the magnet, this force is influenced, providing movement of the ferromagnetic core. This movement is transferred via a rod imposing the out-of-plane displacements in the reflective deformable membrane. In the actuator design a match is made between the negative stiffness of the magnet and the positive stiffness of the membrane suspension. If the locality of the influence functions, mirror modes as well as force and power dissipation are taken into account, a resonance frequency of 1500 Hz and an overall stiffness of 1000 N/m for the actuators is needed. The actuators are fabricated and the dynamic response tested in a dedicated setup. The Bode diagram shows a first eigenfrequency of 950 Hz. This is due to a lower magnetic force than expected. A Helmholtz coil setup was designed to measure the differences in a large set of permanent magnets. With the same setup the 2 nd quadrant of the B-H curve is reconstructed by stacking of the magnets and using the demagnetization factor. It is shown that the values for Hc and Br of the magnets are indeed lower than the values used for the initial design. New actuators, with increased magnet thickness, are designed and currently fabricated.

Systems-in-foil are a new class of electronics in which a full system is integrated into a flexible end product. In this paper, we discuss current research activities and state-of-the-art in this field. Furthermore, some of the associated and expected reliability issues will be addressed on the basis of three examples. As a first example we discuss a flexible large area polymeric organic light-emitting (OLED) device. The reliability targets of these devices require protection against the detrimental influence of water. As a second example, we describe a technology for embedding thinned Si chips between polymeric foils where a careful selection of the base materials is important to account for thermal expansion differences. Finally, as a third example, a novel technology for embedding conductive circuitry in a polymeric foil is discussed in which a good matching of the elastic moduli of the polymeric foil and the embedded circuitry is crucial for the flexibility robustness.

MIRI (the Mid InfraRed Instrument) is one of the focal plane instruments of the James Webb Space Telescope. The instrument comprises a camera and a spectrometer module. The instrument plays the following key roles in the JWST science program. Discovery of the "first light". Assembly of galaxies: history of star formation, growth of black holes, production of heavy elements. Formation of stars and planetary systems. Evolution of planetary systems and conditions for life. The MIRI spectrometer covers the spectral range from 5 - 28.3 μm with a spectral resolution better than 2000. The spectral module is an imaging spectrometer with a field of view ≥ 3 arcsec. The spectrometer consists of 4 spectral channels that share 2 detectors of 1024 × 1024 pixels each. In a single measurement one third of the wavelength range of the channels is imaged onto the detectors. By changing gratings the whole spectral range is covered in 3 measurements. In this paper the optical design of the MIRI spectrometer is described.

The stellarator W7-X will be capable of running in a quasicontinuous operating mode with 10 MW of electron cyclotron heating (ECRH) heating for 30 min, the duration only being limited by the capacity of the available cooling reservoir. The integrated ten discrete water cooled divertor modules need to be closely monitored by ten high resolution infrared imaging (Δx∼10 mm) real time control systems to prevent local overheating which could lead to a destruction of the tiles. Filter based (Hα, C II, C III, etc.) visible imaging systems will initially be used to study divertor symmetry. A first design study of a 2 m long combined IRvisible mirror based endoscope compatible with the boundary conditions of ∼107° viewing angle, thermal vessel movements, front end heat loads of ∼50-100 kW m2, and maximum ECRH stray radiation levels of 50 kW m2 has been performed. The system will be bakeable and contain an integrated shuttercalibrator. A 45° mirror in front of the secondary mirror of the back-end Cassegrain optics gives extra flexibility to install further optical components, e.g., a vessel illumination system, a relative calibration light source, and spectroscopic systems such as a coherence imaging spectrometer or fiber optically coupled grating spectrometers, a scanning laser for an active IR diagnostic, or possibly even an erosion monitor.

The ITER core charge exchange recombination spectroscopy (core CXRS) diagnostic system is designed to provide experimental access to various measurement quantities in the ITER core plasma such as ion densities, temperatures and velocities. The implementation of the approved CXRS diagnostic principle on ITER faces significant challenges: First, a comparatively low CXRS signal intensity is expected, together with a high noise level due to bremsstrahlung, while the requested measurement accuracy and stability for the core CXRS system go far beyond the level commonly achieved in present-day fusion experiments. Second, the lifetime of the first mirror surface is limited due to either erosion by fast particle bombardment or deposition of impurities. Finally, the hostile technical environment on ITER imposes challenging boundary conditions for the diagnostic integration and operation, including high neutron loads, electro-magnetic loads, seismic events and a limited access for maintenance. A brief overview on the R&D and design activities for the core CXRS system is presented here, while the details are described in parallel papers. © 2011 Elsevier B.V. All Rights Reserved.

In preparation for future atmospheric space missions a consortium of Dutch organizations is performing design studies on a nadir viewing grating-based imaging spectrometer using OMI and SCIAMACHY heritage. The spectrometer measures selected species (O3, NO2, HCHO, H2O, SO 2, aerosols (optical depth, type and absorption index), CO and CH4) with sensitivity down to the Earth's surface, thus addressing science issues on air quality and climate. It includes 3 UV-VIS channels continuously covering the 270-490 nm range, a NIR-channel covering the 710-775 nm range, and a SWIR-channel covering the 2305-2385 nm range. This instrument concept is, named TROPOMI, part of the TRAQ-mission proposal to ESA in response to the Call for Earth Explorer Ideas 2005, and, named TROPI, part of the CAMEO-proposal prepared for the US NRC decadal study-call on Earth science and applications from space. The SWIR-channel is optional in the TROPOMI/TRAQ instrument and included as baseline in the TROPI/CAMEO instrument. This paper focuses on derivation of the instrument requirements of the SWIR-channel by presenting the results of retrieval studies. Synthetic detector spectra are generated by the combination of a forward model and an instrument simulator that includes the properties of state-of-the-art detector technology. The synthetic spectra are input to the CO and CH4 IMLM retrieval algorithm originally developed for SCIAMACHY. The required accuracy of the Level-2 SWIR data products defines the main instrument parameters like spectral resolution and sampling, telescope aperture, detector temperature, and optical bench temperature. The impact of selected calibration and retrieval errors on the Level-2 products has been characterized. The current status of the SWIR-channel optical design with its demanding requirements on ground-pixel size, spectral resolution, and signal-to-noise ratio will be presented.

Field of view (FOV) restrictions are known to impair human performance for a range of different tasks. However, the effects of FOV restrictions on human locomotion through a complex environment are still not clear. This is particularly important for the development and deployment of FOV restricting devices like Head Mounted Displays (HMD’s), which generally have FOV’s that are much smaller than the unrestricted FOV. We investigated the effects of both horizontal and vertical FOV restrictions on the walking speed and head movements of participants manoeuvring through complex 3D obstacle courses. All FOV restrictions tested significantly increased the time needed to complete the courses, compared to the unrestricted condition. The time needed to traverse a course was significantly longer for a vertical FOV of 18° than for a vertical FOV of 48°. For a fixed vertical FOV size, the traversal time was constant for horizontal FOV sizes ranging between 75° and 180°, and increased significantly for the 30° horizontal FOV condition. The implications of the current findings for the development of devices with FOV restrictions (like HMD’s) are discussed. Keywords: field-of-view, locomotion, maneuvering

Designing a novel optical system is a nested iterative process. The optimization loop, from a starting point to final system is already mostly automated. However this loop is part of a wider loop which is not. This wider loop starts with an optical specification and ends with a manufacturability assessment. When designing a new spectrometer with emphasis on weight and cost, numerous iterations between the optical-and mechanical designer are inevitable. The optical designer must then be able to reliably produce optical designs based on new input gained from multidisciplinary studies. This paper presents a procedure that can automatically generate new starting points based on any kind of input or new constraint that might arise. These starting points can then be handed over to a generic optimization routine to make the design tasks extremely efficient. The optical designer job is then not to design optical systems, but to meta-design a procedure that produces optical systems paving the way for system level optimization. We present here this procedure and its application to the design of TROPOLITE a lightweight push broom imaging spectrometer. © 2014 SPIE.

The present research is part of an effort to develop tools that make the lens design process more systematic. In typical optical design tasks, the presence of many local minima in the optical merit function landscape makes design non-trivial. With the method of Saddle Point Construction (SPC) which was developed recently ([F. Bociort and M. van Turnhout, Opt. Engineering 48, 063001 (2009)]) new local minima are obtained efficiently from known ones by adding and removing lenses in a systematic way. To illustrate how SPC and special properties of the lens design landscape can be used, we will present the step-by-step design of a wide-angle pinhole lens and the automatic design of a 9-lens system which, after further development with traditional techniques, is capable of good performance. We also give an example that shows how to visualize the saddle point that can be constructed at any surface of any design of an imaging system that is a local minimum.

We present innovative, immersed grating based optical designs for the SMO (Spectrograph Main Optics) module of the Mid-infrared E-ELT Imager and Spectrograph, METIS. The immersed grating allows a significant reduction of SMO volume compared to conventional echelle grating designs, because the diffraction takes place in high refractive index silicon. Additionally, using novel optimization techniques and technical solutions in silicon micromachining offered by the semiconductor industry, further improvements can be achieved. We show optical architectures based on compact, double-pass Three Mirror Anastigmat (TMA) designs, which appear advantageous in terms of one or several of the following: optical performance, reduction of volume, ease of manufacturing and testing. We explore optical designs, where the emphasis is put on manufacturability and we investigate optical solutions, where the ultimate goal is the highest possible optical performance. These novel, silicon immersed grating based design concepts are applicable for future earth and space based spectrometers.

For the Wendelstein 7-X stellarator, which will allow quasicontinuous operation (τ30 min) with 10 MW of electron cyclotron radiation heating power, a conceptual design study for an IR/visible viewing system (IVVS) has been elaborated. Ten such systems, as part of the machine protection system, will be required for real time monitoring of all ten discrete, water cooled divertor modules with high spatial (<10 mm) resolution, in order to prevent local overheating of the target tiles, which could easily lead to their destruction. On the physics side, the systems will be used for divertor symmetry investigations by studying the power load distribution on all targets modules and by observing the island divertor plasmas in the light of Hα, C II, and C III using the visible imaging section of the systems. The optics of the system can be divided into three parts: a mirror based optical head, creating an intermediate image, a Cassegrain telescope system, and individual lens based imaging optics adapted to the various detectors for IR (3-5 μm and 8-14 μm) and visible observations, with their optical light paths being separated by in-vacuum dichroic beam splitters.

In the last years, much interest has grown around the concept of optical surfaces employing high contrast dielectric resonators. However, a systematic approach for the design of this optical surfaces under particular requirements has never been proposed. In this contribution, we describe this approach applied to the robust design of an array of microlenses characterized by a numerical aperture of NA=0.19 with a field of view of FOV = ±60 mrad in a bandwidth of 20 nm. Typically, dielectric resonators are engineered in such a way to have almost full transmissive surfaces with locally tunable phase. However, considering the multiple wavelengths and angles under which the lenses may work, it is difficult to get uniform transmission characteristics for all the dielectric resonators employed. The design strategy, here proposed, uses a particle swarm optimization routine to find the best resonator distribution able to meet the requirements considering the amplitude and phase dispersive characteristics of the resonators surfaces. In the optimization process, also the effects of possible manufacturing inaccuracies, such as variations of resonators radii, are taken into account, allowing a robust design of the structure, within the given manufacturing tolerances. Different designs, operating at 405 nm and 635 nm, are presented and their performances are discussed.