ABSTRACT
Endoscopic techniques are broadly used in medicine. Small diameter endoscopes are either made as fiber bundles or, beneficially, as graded index lenses. Fiber bundles can withstand a mechanical load during their use but the GRIN lens's performance can be affected by its deflection. Here, we analyze the effect of deflection on the image quality and unwanted associated effects with relation to the eye endoscope we designed and built. We also present the result of our effort to make a reliable model of a bent GRIN lens in the OpticStudio software.
Subject(s)
Lens, Crystalline , Lenses , Endoscopy/methods , Endoscopes , Equipment DesignABSTRACT
Optical systems are traditionally used for accurate recording and measurement of the real world's appearance. Present techniques allow us to form a computer-based virtual world, which is used in a variety of technical fields. The crucial issue for future applications of virtual reality is the fidelity of rendered images to real-world objects. This is strongly affected by the appearance of the rendered object's surfaces. Currently, the most applied method of describing a surface's visual appearance of spatially nonuniform surfaces is bidirectional texture function (BTF). We have designed, optimized, built, and tested a unique portable instrument based on a rotary kaleidoscope principle for BTF acquisition in situ. To the best of our knowledge, such an instrument has never been used before to measure BTF of a surface. We enhanced a common static kaleidoscope by adding rotation, which allows us to get a larger number of images of the sample for more combinations of illumination directions and viewing directions. This results in a higher directional and spatial resolution of measured BTF data. In this paper, we focus on the optomechanical design of the rotary BTF measurement instrument and issues related to its alignment to keep the desired mechanical precision.
ABSTRACT
We propose a miniaturised light stage for measuring the bidirectional reflectance distribution function (BRDF) and the bidirectional texture function (BTF) of surfaces on site in real world application scenarios. The main principle of our lightweight BTF acquisition gantry is a compact hemispherical skeleton with cameras along the meridian and with light emitting diode (LED) modules shining light onto a sample surface. The proposed device is portable and achieves a high speed of measurement while maintaining high degree of accuracy. While the positions of the LEDs are fixed on the hemisphere, the cameras allow us to cover the range of the zenith angle from 0 ∘ to 75 ∘ and by rotating the cameras along the axis of the hemisphere we can cover all possible camera directions. This allows us to take measurements with almost the same quality as existing stationary BTF gantries. Two degrees of freedom can be set arbitrarily for measurements and the other two degrees of freedom are fixed, which provides a tradeoff between accuracy of measurements and practical applicability. Assuming that a measured sample is locally flat and spatially accessible, we can set the correct perpendicular direction against the measured sample by means of an auto-collimator prior to measuring. Further, we have designed and used a marker sticker method to allow for the easy rectification and alignment of acquired images during data processing. We show the results of our approach by images rendered for 36 measured material samples.
ABSTRACT
Recent developments in optoelectronics and material processing techniques make it possible to design and produce a portable and compact measurement instrument for bidirectional texture function (BTF). Parallelized optics, on-board data processing, rapid prototyping, and other nonconventional production techniques and materials were the key to building an instrument capable of in situ measurements with fast data acquisition. We designed, built, and tested a prototype of a unique portable and compact multi-camera system for BTF measurement which is capable of in situ measurement of temporally unstable samples. In this paper, we present its optomechanical design.
ABSTRACT
BACKGROUND: Sepsis belongs among the most serious conditions and animal models of sepsis are the basic tools to investigate the pathophysiological response to this condition. MATERIAL AND METHODS: A total of 16 adult minipigs with identical baseline parameters were randomized into two groups. In the sepsis group (n = 10), sepsis was induced using caecal ligation and puncture (CLP). The control group (n = 6) underwent laparotomy without CLP. Selected clinical and laboratory parameters as well as histological findings between the sepsis and control group were subsequently compared. RESULTS: All animals undergoing CLP developed diffuse peritonitis and sepsis. Compared to the control group, experimental animals showed significant increase of body temperature and heart rate (while) requiring noradrenaline to maintain their perfusion pressure. No significant differences in the monitored biochemical parameters (including C-reactive protein levels) between the two groups were found. Histological findings in organs of experimental animals were consistent with changes of organs seen in sepsis, i.e., centrilobular liver necroses, acute tubular renal necrosis, serous fibrinopurulent exudate, myocardial malacias, and pulmonary edema. CONCLUSION: Experimental caecal ligation with a predefined size of the perforation in the intestinal wall is a suitable model for assessing the pathophysiological changes occurring in the body in sepsis.
