Optical Systems Design (original) (raw)
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Applied Optics, 1999
Optical coatings are designed and produced for the Infrared Atmospheric Sounding Interferometer meteorological space instrument operating in the spectral range 3.5-15.5 m. First we discuss the choice of substrates and determine the complex refractive indices of thin-film materials. Then several theoretical solutions are studied for optimizing the efficiency of the instrument. To allow us to study the feasibility of the coatings, a specific mid-infrared optical monitoring system has been developed. This system is validated by the successful manufacture of two-cavity Fabry-Perot filters.
Visible and near-infrared filters for miniaturized spectrometers
2008
The development of lightweight instrumentation for space-based measurements, involves an improvement in the production techniques of optical components. In this work the design and manufacturing of small-dimension variable filter is described. These visible-infrared filters are designed to be coupled to an array detector, in a way that each CCD line is able to detect the radiation in a different narrow radiation band. In this way a compact low-mass optical sensor is obtained that will be combined to a telescope for image spectrometry from space. The optical filters were manufactured by radiofrequency magnetron sputtering, with the aid of a masking system inside the vacuum chamber. Testing at cryogenic temperature proved their stability in the space environment conditions.
Multilayer coatings for multiband spectral observations
International Conference on Space Optics — ICSO 2006, 2017
Extreme UltraViolet instrumentation often requires the use of multilayer coated optics. Such coatings have a limited working bandwidth, and therefore are optimized to perform in correspondence of specific EUV spectral lines. Nevertheless, contemporary observations of the same target in other spectral region would strongly improve scientific knowledge. In this work we present a study on multilayers optimized to achieve high efficiency also in other spectral bands. These coatings would allow the realization of very compact instruments, such as UVCI on board of the Solar Orbiter.
Multilayer Coatings for Metis Instrument
… Conference on Space …, 2010
The Multi Element Telescope for Imaging and Spectroscopy (METIS) is a coronagraph onboard of Solar Orbiter. It will perform simultaneous observations at HeII Lyman-α line, HI Lyman-α line and in visible. To achieve such capability, instrument mirrors need to be coated by multilayer (ML) structures with high efficiency at all three spectral ranges. Coatings with higher performances with respect standard Mo/Si are desirable. An instrument prototype of METIS has just flown onboard of a NASA sounding rocket: in this case, optics were coated with Mg/SiC MLs. Better performances have been obtained in terms of reflectivity, but long term stability of this coating is an open problem. Moreover the harsh conditions of the environment met during the Solar Orbiter mission given by plasma particles and high temperature could affect the lifetime of the optical components on the long term. We present the design and reflectivity tests of multilayer structures in which performances improvement is obtained by the use of novel capping layers. All multilayers are tuned at 30.4nm line but the design also maximize the performances at 121.6nm and 500 -650 nm visible range. Analysis of Solar Orbiter environment have been carried on in order to point out the main damaging sources for the nanostructures. Computer simulations with a devoted software have been performed to preliminary evaluation of the possible instabilities in multilayers. Experimental tests for investigating the effects of the thermal heating and particles bombardments in the reflectivity performances have been planned.
Optical and Mechanical Properties of Layered Infrared Interference Filters
Sensors
The design and manufacturing technology of interference-absorbing short-wave filters based on a layered composition of Si–SiO on a sapphire substrate of various shapes was developed. A transition layer of SiO was applied to the surface of the substrate, alternating with layers of Si–SiO with an odd number of quarter-wave layers of materials with high (Si) and low refractive indices (SiO), and the application of an outer layer of SiO as an appropriate control of the materials’ thickness. The optical properties of the infrared light filter were studied. It was established that the created design of the light filter provides the minimum light transmission in the visible region of the spectrum from 0.38 to 0.78 µm and the maximum in the near infrared region from 1.25 to 5 µm and has stable optical indicators. A method for studying the stress–strain state and strength of a multilayer coating of a light filter under the action of a local arbitrarily oriented load was developed. For simpli...
Thin-film filters for a high resolution miniaturized spectrometer
2008
A lightweight and compact spectrometer with spectral resolution in the order of 0.1 nm, in a spectral range from UV to NIR, can be implemented using a spectral pre-selection technique at the spectrometer entrance, through transmission variable filters. Such filters, based on thin-film optical coatings, have either a transmission peak or a transmission edge that moves along one direction of the filter surface. Depending on the spectrometer design, different configurations of the pre-selection device are possible. The operating spectral range (240-800 nm) is divided in a number of sub-ranges and in each of them the filter transmission peak, or edge, is displaced from the minimum to the maximum wavelength over a distance of few mm. Two cases are considered: a configuration with both a narrow-band transmission filter and a band-pass filter having a linear spatial variation and a configuration with an edge filter having a non-linear spatial variation. To obtain the required spatial profile of filter performance, a graded coating is deposited on a fused silica substrate, by r.f. sputtering with a moving mask. Details on filter requirements and fabrication technology are reported.
Development of multilayer thin film filters for the full-sun imager on Solar Orbiter
Solar Physics and Space Weather Instrumentation IV, 2011
Membranes a few hundred nanometers thick are used in EUV optics to make, for example, beams splitters or passband filters. Despite their necessity in numerous applications these components are, because of their thinness, extremely fragile and their implementation in space instruments is always difficult. The authors are developing thin film filters for the Full Sun Imager, one of the EUV telescopes on board the Solar Orbiter mission with objectives of high optical efficiency and mechanical strength. These filters are specifically designed to isolate one or the other of the two passbands (17.4 and 30.4 nm) reflected by the telescope's dual band mirror coating. In this paper we present the optical properties of the prototype components.
Study on spectral shift of infrared multilayer thin film filters by using of equivalent index locus
Physics Procedia, 2011
Spectral shift of infrared multilayer thin film filters, which use lead telluride and zinc sulfide as thin film materials, when used under cryogenic circumstance, was investigated. As the index of lead telluride varies with the change of temperature, its influence on the performance of filter must be taken into consideration when there is a temperature difference between preparation and application circumstance. A shift model was established on the basis of interlayer compensating effect of multilayer thin films, value of wavelength shift was calculated using equal dividing method, and the calculated result is well coincident with the measured one.
Space-exposure effects on optical-baffle coatings at far-infrared wavelengths
Applied Optics, 1992
Reflectance of six optical-black coatings was remeasured over the near-infrared to the far-infrared region after nearly 6 years in space aboard the Long Duration Exposure Facility satellite. Measurements were made at room temperature and at cryogenic temperatures. The most notable effect was a general decrease in reflectance for typical samples at all wavelengths. Analysis indicates that this decrease is caused by an increase in absorption resulting from an increase in the imaginary part of the index of refraction, and not by a change in thickness, or increased surface roughness giving rise to increased scattering. These results suggest that such optical-baffle materials will provide enhanced performance as a result of aging in the space environment.