The activity "Virtual Reality applied to Teletesting" is related to a wider European Space Agency (ESA) initiative of cost reduction, in particular the reduction of test costs. Reduction of costs of space related projects have to be performed on test centre operating costs and customer company costs. This can accomplished by increasing the automation and remote testing ("teletesting") capabilities of the test centre.
Main problems related to teletesting are a lack of situational awareness and the separation of control over the test environment. The objective of the activity is to evaluate the use of distributed computing and Virtual Reality technology to support the teletesting of a payload under vacuum conditions, and to provide a unified man-machine interface for the monitoring and control of payload, vacuum chamber and robotics equipment.
The activity includes the development and testing of a "Virtual Reality Teletesting System" (VRTS). The VRTS is deployed at one of the ESA certified test centres to perform an evaluation and test campaign using a real payload. The VRTS is entirely written in the Java programming language, using the J2EE application model. The Graphical User Interface runs as an applet in a Web browser, enabling easy access from virtually any place.
Purpose: Local variations in refractive index are an important physical cause of light scattering in the lens. The goal of this study was to further add to the understanding of the process of light propagation in the lens by directly measuring local variations in refractive index by phase contrast microscopy. Methods: Refractive index was estimated by immersion refractometry. Cryo-sections of quick frozen human donor lenses were embedded in a graded series of bovine serum albumin solutions, and in immersion oil. Results: Superficial cortical fiber membranes proved to have a refractive index considerably above values given for cytoplasm at the same location. Nuclear fiber membranes have a refractive index of the same order as given in the literature for nuclear fiber cytoplasm. Conclusion: The large difference in refractive index between fiber membranes and cytoplasm in the lens cortex may be important for optical function and transparency of the lens. Support: Marie Curie Fellowship of the European Community program Quality of Life (QLK6-CT-1999-51159).
Recent data in the literature on psychophysically determined in vivo intraocular straylight, and on in vitro fluorescence of the eye lens are analyzed. From the psychophysical straylight data, light scattering changes in the lens due to normal aging and age-related cataract formation are derived in physical terms. The intensities of these light-scattering changes prove to follow approximately cu p (u=scatter angle) with p'−2 and c dependent on age and cataract. Both p and c are in accordance with recent in vitro studies on light scattering using donor lenses. Fluorescence of the lens causes light with wavelengths of 420 nm and lower to be in total
visually much more effective: by a factor of 2.7 to 6.8 at 400 nm, and a factor of 71 to 151 at 380 nm. Because fluorescence adds a homogeneous veil to the point spread function, for some visual effects (e.g., glare) the increase can be (much) larger.
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