A simple design of uniform LED illumination using catadioptric collimator and freeform lenslet array

We introduce a compact lenslet array principle that takes advantage of freeform optics to deploy a light distributor, beneficial for highly efficient, inexpensive, low energy consumption light-emitting diode (LED) lighting system. We outline here a simple strategy for designing the freeform lens that makes use of an array of the identical plano-convex lenslet. The light is redistributed from such lenslet, hinging on the principle of optical path length conservation, and then delivered to the receiver plane. The superimposing of such illumination area from every lenslet occurs on the receiver plane, in which the non-uniform illumination area located in the boundary should have the same dimension as the size of the freeform lenslet array. Such an area, insofar, is negligible due to their small size, which is the crux of our design, representing a large departure from the former implementations. Based on simulations that assess light performance, the proposed design exhibited the compatibility for multiple radiation geometries and off-axis lighting without concern for the initial radiation pattern of the source. As simulated, the LED light source integrated with such proposed freeform lenslet array revealed high luminous efficiency and uniformity within the illumination area of interest were above 70% and 85%, respectively. Such novel design was then experimentally demonstrated to possess a uniformity of 75% at hand, which was close to the simulation results. Also, proposed indoor lighting was implemented in comparison with the commercial LED downlight and LED panel, whereby the energy consumption, number of luminaires and illumination performance were assessed to show the advantage of our simplified model.

Comparative Analysis of Some Schell-Model Beams Propagating Through Turbulent Atmosphere

In this paper, we investigate a comparative analysis of some Generalized Laguerre-Gaussian Schell-model beams through a paraxial ABCD optical system in a turbulent atmosphere. Based on the extended Huygens-Fresnel diffraction integral, analytical expressions for the spectral density in the receiver plane of the studied beams are derived in detail. By studying the effects of the source coherence parameters and the atmospheric turbulence strength, the numerical results indicate that the profile of these Schell-model beams takes different shapes during their propagation.

Study on the Optical Properties of the Point-Focus Fresnel System

The characteristic analysis of the flux formed by the heliostat in the optical system is the basis in design and optimization of the whole system. In this paper, our research subject is a pilot installation of the point-focus Fresnel system, which is a new optical design between the tower system and the dish system. For the optical system, it is very important to accurately calculate the solar flux density distribution on the receiver plane. Aiming at the case that the focal length of the heliostat is not equal to the distance from the center of the heliostat to the center of the receiver plane, based on the projection, an approximate calculation method is proposed. Using the method to calculate the solar flux density distribution of the point-focus Fresnel system, and the results are compared with that calculated by SolTrace code, it is found that the solar flux density distribution of both is relatively consistent in shape and numerical value, which verifies the accuracy of the method and it can be used for design and optimization of the point-focus Fresnel system.

Li-Pos: A Light Positioning Framework Leveraging OFDM for Visible Light Communication

The design of solid-state lighting is vital, as numerous metrics are involved in their exact positioning, and as it is utilized in various processes, ranging from intelligent buildings to the internet of things (IoT). This work aims to determine the power and delay spread from the light source to the receiver plane. The positions of the light source and receiver were used for power estimation. We focus on analog orthogonal frequency-division multiplexing (OFDM) in visible light communication (VLC) and assess the area under the curve (AUC). The proposed system was designed using modulation techniques (i.e., quadrature amplitude modulation; QAM) for visible light communication (VLC) and pulse-width modulation (PWM) for dimming sources. For the positioning and spreading of brightness, the proof-of-concept was weighted equally over the entire area. Therefore, the receiver plane was analyzed, in order to measure the power of each light-emitting diode (LED) in a given area, using the delayed mean square error (MSE). A framework was applied for the placement of LEDs, using full-width at half-maximum (FWHM) parameters with varying distances. Then, the received power was confirmed. The results show that the AUC using DRMS values for LEDs significantly increased (by 30%) when the number of source LEDs was changed from four to three. These results confirm that our system, associated with the simple linear lateration estimator, can achieve better energy consumption.

Effect of Receiver’s Tilted Angle on the Capacity for Underwater Wireless Optical Communication

This paper focuses on the effect of the receiver’s tilted angle on the capacity of a clear ocean water Underwater Wireless Optical Communication (UWOC) system. To achieve this goal, the relationship between the channel capacity and the receiver’s tilted angle is investigated. First, we propose a double-exponential fading model with pointing error which can more accurately depict the channel of clear ocean water UWOC instead of the traditional Beer’s law model. Based on this channel model, we present the close-form expression of the capacity bounds of the UWOC system. Then, an optimization problem is formulated to improve the capacity by tilting the receiving plane. Both theoretical analyses and simulation results verify that the capacity bounds of UWOC can be enhanced dramatically by tilting the receiver plane at an optimal angle. Thus, in practice, we can provide an effective design strategy for a UWOC system.

A receiver intensity for Super Lorentz Gaussian beam (SLG) propagation via the moderate turbulent atmosphere using a novelty mathematical model

First of all, the beam propagation of Super Lorentz Gaussian (SLG) profile is propagated via space, the recent research dealt extensively with the investigation of the propagation of SLG in a level of specified atmospheric. In a turbulent atmosphere of intensity and receiver field, models were derived from a new mathematical expression of intensity and analyzed. Also, to find the power scintillation indicators for the SLG beam in a random turbulence of receiver plane. The equations are obtained for the average receiver-aperture. The new beam of SLG systems generated a modified model when compared with the receiver-aperture averaging. When we revisions the parameters, firstly is started the factor source size, this affected the profile for the power propagation and the analysis proved that the average of the aperture is affected by increasing the distance of propagation length. The enhancement of the average power of the aperture effect reliably with the source size of the initial beam source depends on several factors, including the structure constant, the beam order and static value of source size. Finally, the target of this article is detected a novel of mathematical expression of the receiver intensity is applied in the system of optical communications.

On seismic deghosting using Green’s theorem

We have examined theoretically how receiver-side deghosting of pressure measurements can be derived from the Green’s theorem method. We split the Green’s function that obeys Dirichlet boundary conditions on the sea surface and at the receiver plane into two contributions: the first emitting energy downward only from its source location and the other emitting energy only upward. Using the normal derivative of the source-side downgoing Green’s function in the Green’s theorem evaluation over the receiver plane, the upgoing part of the pressure field is predicted. This is the receiver-side deghosted field. By inserting the source-side upgoing normal derivative Green’s function in Green’s theorem, its evaluation over the receiver plane predicts the downgoing part of the pressure field. For a plane horizontal receiver surface, the required Green’s function can be derived using the image series expansion method. To display the fundamental frequencies of this Green’s function, we have applied a Fourier series expansion of the Green’s function. Our theory gives a new understanding of and generalizes and simplifies previously published theories on Green’s theorem-based receiver-side deghosting of pressure wavefields.

Alignment Strategy Optimization Method for Dish Stirling Faceted Concentrators

A Dish Stirling parabolic concentrator typically consists of a number of mirror facets that must be aligned to focus the concentrated sunlight on the engine receiver. An alignment strategy must be developed to deliver the energy uniformly to the receiver while maximizing system performance. Several criteria must be met in order to maximize the performance and lifetime of the system. The peak flux should be minimized at the receiver to extend life. This is accomplished by locally optimizing the mirror aimpoints, minimizing overlap of facet images. The energy delivered to each cylinder of a multi-cylinder engine should be balanced to maximize the power production capability of the engine. This is accomplished through globally optimizing the mirror aimpoints. Depending on dish geometry, both of these constraints will be met by moving the aimpoints of certain facets away from a single point at the center of the aperture. However, this often results in a larger aperture or more flux spillage. The larger aperture results in greater thermal and reflective losses from the receiver cavity. This paper proposes and demonstrates a novel approach to optimizing the alignment strategy while obeying these constraints. The method uses an approach similar to molecular dynamics to globally and locally distribute the power on the receiver, while imposing movement constraints at the aperture to limit the focal plane spot size. The method can also impose additional geometric constraints at the receiver plane to accommodate un-cooled surfaces. The method is explored and demonstrated on the Stirling Energy Systems 25kW dish Stirling system at Sandia National Laboratories. The approach provides a receiver flux distribution and power balance equal to the strategy developed by McDonnell Douglas in the early 1980’s, but with an aperture size equal to that of the single aimpoint strategy. This should result in about a 1kW increase in power generated at rated conditions, with no additional cost, due to reduced thermal losses from the receiver. The method can be extended to other point-focus concentrating solar technologies. On a tower, the heliostat aiming strategy could be dynamically updated to accommodate flux profile needs, sun position, or maintenance in the field.