This paper considers the use of infrared wireless communications for uplink transmission in extra wireless body-area networks. We focus on a multiuser medical application, where the collected medical data of several patients inside a hospital room is transmitted to one or several access points (APs). For this uplink transmission, we investigate the performance of optical code-division multiple access in asynchronous mode, while taking into account the effect of random transmitter orientation. For this purpose and to consider realistic scenarios, we implement an orientation-based random waypoint mobility model to consider the mobility of patients inside a hospital ward. Performance evaluation is done in terms of the link average bit-error-rate and outage probability. We further investigate the performance improvement by using several APs, compared with the case of a single AP. INDEX TERMS Wireless body area networks; Medical WBAN; Telemedicine; Wireless optical communications; Infrared data transmission; Optical code-division multiple access; Random waypoint model; Binary pulse-position modulation.
A lens limited by diffraction and having two parabolic surfaces is presented. The knowledge of the following parameters: object distance, relative refractive index, lens thickness, and image distance, enables to analytically calculate the parabolic front and back surfaces. The conditions to obtain diffraction-limited images for these lenses and its maximal diameter are described. These bi-parabolic lenses can be easily manufactured at reduced costs and can be used for several commercial and industrial applications. The method to obtain such surfaces and a simple example validated by using Oslo® are described here.
Lens design uses a calculation of the lens' surfaces that permit to obtain an image from a given object. A set of general rules and laws permits to calculate the essential points of the optical system such as distances, thickness, pupils, and focal distance among others. Now, the theory on which the classical lens design is based changes radically as our theoretical foundations do not rely on the classical ray tracing rules. We show that with the rules expressed in a reduced vector analytical solution set of equations, we can take into account all optical elements, i.e. refractive, reflective, catadioptric. These foundations permit to keep under control the system aberration budget in every surface. It reduces the computation time dramatically. The examples presented here were possible because of the versatility of this theoretical approach. IntroductionGeometrical optic allows us to design optical systems by simply drawing a couple of rays having an object as the origin and an image as the final destination. These rays are called the chief ray and the marginal ray. The marginal ray departs from the most representative object point; it lies on the optical axis, travelling through the diaphragm edge. The chief ray departs from the outermost object point travelling through the diaphragm's center as shown in figure 1(a). Classical paraxial chief and marginal rays allow one to calculate the higher-order aberrations to control the image quality at large F-numbers. Thus, it is a starting point design for optimization of fast rotationally symmetric systems. Nonetheless, the classical paraxial theory has limitations when used to design systems with freeform surfaces. We should point out that all orders of spherical aberration cannot be controlled using the two-rays approach. However, in a high order approximation, all other classical types of aberrations can be examined. The higher order spherical aberration is mostly occurring in high numerical apertures or low F-number applications. In the case of wideangle, large field-of-view applications, and refined chromatic corrections, the higher-order contributions of other aberrations are also relevant. Here we show a theory to design optical systems when compared to the classical geometrical optics one. This theory allows us maintain under control all the aberrations in freeform optical systems.The model does not have a fixed coordinate system. It depends on the optical paths and there is a single analytical solution that permits for the design of complex optical systems. Ray tracing can be used for assessment. The complete set of equations used in geometrical optics is replaced by a reduced set of vector formulas. This foundation can be easily explained and applied computationally.Geometrical optics is based in drawing rays from an arbitrary point in an object to the corresponding point in an image after crossing through the optical system. W. Snell and R. Descartes proposed the refraction and reflection laws in a time when vectors did not exist.
We have developed an optical Absolute Distance Meter (ADM) based on the measurement of the phase accumulated by a Radio Frequency wave during its propagation in the air by a laser beam. In this article, the ADM principle will be described and the main results will be presented. In particular, we will emphasize how the choice of an appropriate photodetector can significantly improve the telemeter performances by minimizing the amplitude to phase conversion. Our prototype, tested in the field, has proven its efficiency with a resolution better than 15 μm for a measurement time of 10 ms and distances up to 1.2 km.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.