For the latest SSL projects, go to Completed Research.
Archive Categories
Applications Research and Demonstration
Evaluating White LEDs for Outdoor Lighting Application
Researchers are working to create white light sources that are suitable for outdoor applications such as signage and landscape lighting.
Evaluation of LEDs for Outdoor Signage Application
Outdoor signs commonly are constructed of neon and cold-cathode fluorescent lamps, but interest in using LEDs has been growing because of the potential for greater energy and maintenance savings and improved performance over current technologies. Presently, there are no standards for signage in terms of luminance, brightness uniformity, or life. Therefore, in order to determine the suitability of LEDs for this application, this study evaluated the performance of LEDs in outdoor signage and identified criteria for setting acceptance standards.
Refrigerated Display Case Lighting with LEDs
Using high-brightness LEDs in refrigerated display cases as a replacement for fluorescent lamps is the focus of this study. Solid-state lighting offers light with less heat.
Use of Colored Light in Display Lighting
Using solid-state lighting to provide color in retail display windows helps to attract potential customers. By using colored light on the display background, researchers discovered that they could reduce the percentage of light output of a high-energy accent light in the display without sacrificing visual appeal or the ability to see objects clearly.
Color and Optics
Color and Brightness Discrimination of White LEDs
Little is known about the temporal characteristics of white LEDs on visual perception. Researchers are conducting experiments to gather chromaticity and luminance data of white LEDs over time, and testing subjective discrimination of color and brightness differences.
Optical Elements for Mixing Colored LEDs to Create White Light
This study focuses on evaluating several optical elements through computer software simulation to determine the proper mix of monochromatic LEDs to produce white light.
LED Performance, Reliability, and Life Prediction
Non-contact Method for Determining Junction Temperature in White LEDs
This study investigated a non-contact method of determining the junction temperature of phosphor-converted white LEDs as a first step toward determining the useful life of systems using white LEDs.
Performance Characteristics of High-Power LEDs
A laboratory experiment was conducted to investigate the performance characteristics of currently available high-power LEDs under various drive conditions and ambient temperatures. Light output degradation and color shift properties as a function of time were measured for five types of commercial high-power LEDs.
Performance Characteristics of Light Emitting Diodes
LED packages feature performance characteristics that often vary widely. Designing an LED luminaire involves designing a product with proper drive circuits and heat sinks to ensure quality performance. This project examines performance characteristics in solid-state light sources.
Projecting the Useful Life of LED Lighting Systems
Lighting systems employing LEDs have grown quite popular. However, their increasing usage raises questions regarding the long-term performance of LED systems. This study explored system-appropriate methods for measuring junction temperature, a primary cause of LED degradation, which could then be used to quickly determine the degradation rates of these lighting systems.
Metrics
Color Rendering Index (CRI) for LED Light Sources 
LED light sources are presenting challenges to researchers evaluating their color rendering characteristics. Luminous efficacy, color rendering index (CRI), and life are the three most commonly used metrics to evaluate a light source. Yet, studies show that with LED-based sources, CRI is not a good predictor of color preference. Researchers are working to devise a more reliable metric.
Determining Contrast Sensitivity Functions for LEDs
LEDs are quickly becoming the choice for many lighting applications that require monochromatic light. However, one potential problem with LED-based lighting systems is uneven luminance patterns. A uniform luminance distribution is important in some applications, such as backlighted signage. The objective of this study was to develop a family of contrast sensitivity functions for high-brightness LEDs that could be used to evaluate the luminance uniformity of backlighted signage.
= Project sponsored by ASSIST
|
