Application of light emitting diodes is expanding as the luminous output and efficiencies of these devices improve. At the same time, the number of LED package types is increasing, making it challenging to determine the appropriate device for use in lighting product designs.
A range of factors should be considered when selecting a LED for an application including color coordinates, luminous efficacy, cost, lumen maintenance, application life, packaging and manufacturability. Additional complexities can be introduced as LED packages become obsolete and replacement parts must be selected. The replacement LED characteristics must be understood and assessed against the parameters of the original device, in order to determine if the change will be relatively simple or will force other end-product changes.
While some characteristics are readily measured and compared, other factors, such as lumen maintenance, are difficult to verify. This paper will discuss the characteristics of a LED that should be considered during the design process as well as methods to validate these characteristics, particularly those which are not typically on data sheets or, are critical to the design and warrant additional validation. Particular attention will be given to LED lumen maintenance. While published manufacturer data typically provides temperature versus performance curves, the data may not be useful depending upon the application's operating environment. Models must be created to estimate the LED's junction temperature and degradation curve at the applied temperature in order to develop a more precise life estimate. This paper presents one approach to a LED device life and performance study designed with application environments in mind.
Solid state lighting (SSL) has made substantial inroads into the aviation lighting market in recent years. In many aircraft applications, the unique characteristics of this technology make it superior to the light sources presently employed. However, the novelty of this technology also brings new challenges to successful implementation within rigorous aerospace environs. This paper provides an overview of how the advent of solid state lighting has benefited the aerospace lighting industry, examines some of the current applications and looks forward to future uses of SSL in the aviation market. The discussion will include an examination of aerospace requirements and how SSL technology meets those requirements. The authors will address some of the challenges presented by solid state light relative to the aerospace industry and explore how these issues can be overcome.
As LEDs continue to improve in efficacy and total light output, they are increasingly finding their way in to new applications in the aviation industry as well as adjacent markets. One function that is particularly challenging and may reap substantial benefits from this new technology is the fuselage mounted anti-collision light. Anti-collision lights provide conspicuity for the aircraft by periodically emitting bright flashes of light. The color, light distribution and intensity levels for these lights are all closely regulated through Federal Aviation Regulation (FAR) documents. These lighting requirements, along with thermal, environmental and aerodynamic requirements, drive the overall design. In this paper, we will discuss the existing technologies used in anti-collision lights and the advantages and challenges associated with an LED solution. Particular attention will be given to the optical, thermal, electrical and aerodynamic aspects associated with an LED approach. A specific case study will be presented along with some of the challenges that have arisen during the design process. These challenges include the addition of an integrated covert anti-collision lighting.
Two methods of image display are developed in which the best 5-7 images of the peripheral arteries are joined together to form a single, continuous image of the legs. First, a complete image of both legs, called WHOLE LEG, is reduced so that it fits on a single monitor or hardcopy image. Second, a full resolution image, called SCROLL, is assembled that can be scrolled on a video monitor. From the geometrical parameters of the acquisition (source-to_detector distance, table height, etc.), the portions of each image to remove beforejoining the remaining portions together are estimated. This estimate is refined using an automatic search for the best match. To correct for body taper, images are intensity equalized. Using a reconstruction method that assumes a planar geometry results in a volume that is displayed in neighboring image frames and a volume that is never displayed. Nevertheless, WHOLE-LEG is aesthetically pleasing. In the case of SCROLL, images are displayed such that every part of each input image is displayed at one time or another. A video tape of SCROLL shows how this works.
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