A compact Interferometric Tomograph has flown on a MASER sounding rocket in spring 2002. This original instrument has been developed by Lambda-X (optics) and the Swedish Space Corporation-SSC (electronics) to measure 3-dimentional temperature (through refractive index) distribution in a liquid while it evaporates though a limited free surface. The tomograph includes 6 interferometers arranged symmetrically around a liquid cell. The paper describes the module and concentrates on the optical beam splitting and combining original systems that have been implemented in the compact instrument; holographic gratings are used to split the sole laser beam into 6 beams and to combine the 6 interferometer views on 2 CCD cameras. Finally, 3-dimentional temperature distributions reconstructed from flight data are presented.
The Protein Crystallisation Diagnostic Facility (PCDF) is a multi-user facility to study the protein crystallisation under the conditions of micro-gravity onboard the International Space Station (ISS) Columbus facility. Large size protein crystals will growth under reduced gravity in thermally controlled reactors. A combination of diagnostic tools like video system, microscope, interferometer, and light scattering device shall help to understand the growth phenomena.
The Fluid Science Laboratory (FSL) is a multiuser facility developed and built by the European Space Agency (ESA). Its launch onboard the Columbus Laboratory, a module of the International Space Station (ISS) is foreseen in June 2005 according to the present planning. FSL can host sequentially Experiment Containers dedicated to a specific experiment in various scientific areas like fluid science, crystal growth, foams and directional solidification within transparent media and, owing to its adaptable diagnostic tools and its modularity on several levels, complementary science areas such as colloid and aerosol physics, particle agglomeration and plasma crystals are envisaged. The visualisation, monitoring and control of the experiment is based on a set of optical diagnostics included in the FSL facility such as visualisation in two perpendicular directions, velocimetry, ESPI and Wollaston interferometry, Schlieren working in transmission and reflection modes, infrared and a high speed camera. The paper will describe the optical tools included in FSL and their performances.
As part of the development of an Experiment Container (EC) for the Fluid Science Laboratory (FSL), to be launched to the International Space Station, a digital holographic microscopy (DHM) system has been breadboarded. The scientific topic of this EC is emulsions, and a large depth of field (DOF) is required. The DHM enables to visualise the drops of emulsions, down to a size of 4 μm, on a DOF which is about 90 times its classical value. All this information is contained in one single image, which is a major advantage in space applications, where the downlink datarate and recording capacity are very limited compared to laboratory conditions. This paper describes the technique being used, presents the application to emulsions, shows tests results including image re-construction, and quantifies the performances as well as the limitations of the system.
NIMO is a new measurement tool based on the Phase-Shifting Schlieren technique [1]. The technique combines the Schlieren principle with the phase-shifting technique generally used in interferometry. By an adequate Schlieren filter and an adapted set-up, some Schlieren Fringes coding light beam deviation angles are generated. After the application of the phase shift technique, the Schlieren phase is calculated and converted in beam deviation values. The technique has been validated on conventional optical element ranging from millimetre to decimetre scales. NIMO opens a new step in metrology in a wide industrial range in both reflection and transmission (e.g. optical manufacturing, glass industry, ophthalmic industry,...).
In [2],we focused on fluid physics applications and the implementation of the technique in a microscope for MEMS measurements. In [3], we described an adapted setup in which all the phase shifted images are acquired simultaneously opening the possibility to measure dynamic phenomena with NIMO.
This paper is focused on the instrument recently developed for ophthalmic industry. The performances of the instrument are given and industrial applications in free-form and aspherical surfaces metrology are demonstrated.
A new technique to measure shapes and deformation with a high resolution is proposed. It combines the conventional Schlieren technique principle with the phase-shifting approach generally used in interferometry. By an adequate Schlieren filter and an adapted set-up, some Schlieren Fringes are generated. After the application of the phase shift technique, the Schlieren phase is calculated and converted into beam deviation values, which are integrated to deduce the object's shape. Both theoretical and experimental demonstrations are given. The technique is first validated on a reference target. With a setup working in reflection, we have measured the curvature radius of a lens surface with accuracy better than 1%. Then an application in a fluid physics experiment is given. The shape of a liquid-gas interface in a conventional Marangoni-Benard experiment has been measured with a resolution of 30nm and amplitudes up to 50μm. The shape of MEMS has also been measured in a PSS microscope with a nanometric resolution. Finally, we propose an adaptation of the setup to make it possible the measurement of fast phenomena at video frame rate.
The Fluid Science Laboratory (FSL) to be embarked on board the European Space Agency's Columbus Orbital Facility (COF) as part of the International Space Station (ISS) is a multi-user facility for the performance of microgravity research. It comprises a very complex optical bench, which can be configured in a number of different ways depending on the experiments to be undertaken. In particular several different types of interferometry including Phase-Shift, Electronic Speckle Pattern and Wollaston Shearing are feasible. This provides FSL and the scientists who use it with highly sensitive optical diagnostic tools for fluid physics research under microgravity conditions over extended periods of time. FSL is foreseen to operate on orbit for ten years. In this regard the entire optical bench and its optical components must withstand the launch, microgravity, thermal and radiation environments without significant degradation in performance over that time. The total radiation qualification dose for FSL is relatively low in absolute terms at a value 1400 Rad (14 Gy). It was expected that this would not cause a problem, but prior to these tests there was no quantitative data at all available on the radiation response of most of the optical glasses used, and hence a formal statement of qualification could not be made. This paper presents results of the radiation testing of most of the important glass materials used on the optical bench. The data are presented and analyzed in a parametric way such that the information may be applied to other optical instruments operating in a similar space radiation environment and for intermediate or longer timescales than the nominal FSL end of life of ten years.
Interferometry has always been a powerful tool to diagnose the response of liquids, when changes of status parameters induce modifications in their optical properties. Interferometric measurements are based on the ability to measure variations, around a reference configuration, in the optical path length or the refractive index. Investigations done so far on heat convection driven by capillary forces, indicate that the observation of both the bulk phase and of the free surface, is instrumental for the understanding of the physical mechanisms steering the heat transfer phenomena in 'weightless liquids'. When used in space application, conventional interferometers suffer of some fundamental drawbacks, because of the severe requirements in terms of mechanical stability of the optical elements. Holographic interferometry removes the most stringent limitations of classical interferometry, but requires precise positioning of the recording plate, with accuracy better than half a wavelength. The superior feature of an electronic speckle pattern interferometer (ESPI) is that it enables real time correlation fringes to be recorded by a video camera and displayed on a television monitor, without recourse to any form of photographic processing or plate relocation. This comparative ease of operation allows the technique of ESPI to be extended to considerably more complex problems of deformation analysis and measurement of refractive index modulation. Since it basically works as a time differential interferometer, measurements can always be referred to a well known configuration and condition of the test sample, reducing or even eliminating the requirements on mechanical stability. This paper describes how double-path ESPI are accommodated within the optical diagnostics of a microgravity payload, fluid physics facility, due to launch in 1998 on the Russian retrievable capsule FOTON. The two- ESPI layout permits one to observe and quantify the deformation of the free surface of a liquid subjected to a thermal gradient.Motions induced by the convective flows in the bulk phase can be monitored at the same time. The main features of the ESPI are presented together with design outlines and optical performances.
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