Proc. SPIE. 10378, Sixteenth International Conference on Solid State Lighting and LED-based Illumination Systems
KEYWORDS: Optical components, Light emitting diodes, LED lighting, Solid state lighting, Manufacturing, 3D printing, Additive manufacturing, Printing, Light sources and illumination, Solid state electronics
Low energy use and reduced maintenance have made the LED, a solid-state light (SSL) source, the preferred technology for many lighting applications. With the explosion of products in the marketplace and subsequent price erosion, manufacturers are looking for lower cost materials and manufacturing methods. 3-D printing, also known as additive manufacturing, could be a potential solution. Recently, manufacturers in the automotive, aerospace, and medical industries have embraced 3-D printing for manufacturing parts and systems. This could pave the way for the lighting industry to produce lower cost, custom lighting systems that are 3-D printed on-site to achieve on-time and on-demand manufacturing. One unique aspect of LED fixture manufacturing is that it requires thermo-mechanical, electrical, and optical components. The goal of our investigation was to understand if current 3-D printing technologies and materials can be used to manufacture functional thermo-mechanical, electrical, and optical components for SSL fixtures. We printed heat sink components and electrical traces using an FFF-type 3-D printer with different filaments. The results showed that the printed heat sinks achieved higher thermal conductivity values compared to components made with plastic materials. For electrical traces, graphene-infused PLA showed low resistivity but it is much higher than bulk copper resistivity. For optics, SLA-printed optical components showed that print resolution, print orientation, and postprocessing affect light transmission and light scatter properties. Overall, 3-D printing offers an opportunity for mass customization of SSL fixtures and changing architectural lighting practice, but several challenges in terms of process and materials still have to be overcome.
The organic light-emitting diode (OLED) is an area light source, and its primary competing technology is the edge-lit light-emitting diode (LED) panel. Both technologies are similar in shape and appearance, but there is little understanding of how people perceive discomfort glare (DG) from area sources. The objective of this study was to evaluate the DG of these two technologies under similar operating conditions. Additionally, two existing DG models were compared to evaluate the correlation between predicted values and observed values. In an earlier study, we found no statistically significant difference in human response in terms of DG between OLED and edge-lit LED panels when the two sources produced the same luminous stimulus. The range of testing stimulus was expanded to test different panel luminances at three background illuminations. The results showed no difference in perceived glare between the panels, and, as the background illumination increased, the perceived glare decreased. In other words, both appeared equally glary beyond a certain luminance and background illumination. We then compared two existing glare models with the observed values and found that one model showed a good estimation of how humans perceive DG. That model was further modified to increase its power.
LED products have started to displace traditional light sources in many lighting applications. One of the commonly
claimed benefits for LED lighting products is their long useful lifetime in applications. Today there are many
replacement lamp products using LEDs in the marketplace. Typically, lifetime claims of these replacement lamps are in
the 25,000-hour range. According to current industry practice, the time for the LED light output to reach the 70% value
is estimated according to IESNA LM-80 and TM-21 procedures and the resulting value is reported as the whole system
life. LED products generally experience different thermal environments and switching (on-off cycling) patterns when
used in applications. Current industry test methods often do not produce accurate lifetime estimates for LED systems
because only one component of the system, namely the LED, is tested under a continuous-on burning condition without
switching on and off, and because they estimate for only one failure type, lumen depreciation. The objective of the study
presented in this manuscript was to develop a test method that could help predict LED system life in any application by
testing the whole LED system, including on-off power cycling with sufficient dwell time, and considering both failure
types, catastrophic and parametric.
The study results showed for the LED A-lamps tested in this study, both failure types, catastrophic and parametric, exist.
The on-off cycling encourages catastrophic failure, and maximum operating temperature influences the lumen
depreciation rate and parametric failure time. It was also clear that LED system life is negatively affected by on-off
switching, contrary to commonly held belief. In addition, the study results showed that most of the LED systems failed
catastrophically much ahead of the LED light output reaching the 70% value. This emphasizes the fact that life testing of
LED systems must consider catastrophic failure in addition to lumen depreciation, and the shorter of the two failure
modes must be selected as the system life. The results of this study show a shorter time test procedure can be developed
to accurately predict LED system life in any application by knowing the LED temperature and the switching cycle.
Solid-state lighting (SSL) offers a new technology platform for lighting designers and end-users to illuminate spaces
with low energy demand. Two types of SSL sources include organic light-emitting diodes (OLEDs) and light-emitting
diodes (LEDs). OLED is an area light source, and its primary competing technology is the edge-lit LED panel. Generally,
both of these technologies are considered similar in shape and appearance, but there is little understanding of how people
perceive discomfort glare from large area light sources. The objective of this study was to evaluate discomfort glare for
the two lighting technologies under similar operating conditions by gathering observers’ reactions. The human factors
study results showed no statistically significant difference in human response to discomfort glare between OLED and
edge-lit LED panels when the two light sources produced the same lighting stimulus. This means both technologies
appeared equally glary beyond a certain luminance.
The organic light-emitting diode (OLED) has demonstrated its novelty in displays and certain lighting applications. Similar to white light-emitting diode (LED) technology, it also holds the promise of saving energy. Even though the luminous efficacy values of OLED products have been steadily growing, their longevity is still not well understood. Furthermore, currently there is no industry standard for photometric and colorimetric testing, short and long term, of OLEDs. Each OLED manufacturer tests its OLED panels under different electrical and thermal conditions using different measurement methods. In this study, an imaging-based photometric and colorimetric measurement method for OLED panels was investigated. Unlike an LED that can be considered as a point source, the OLED is a large form area source. Therefore, for an area source to satisfy lighting application needs, it is important that it maintains uniform light level and color properties across the emitting surface of the panel over a long period. This study intended to develop a measurement procedure that can be used to test long-term photometric and colorimetric properties of OLED panels. The objective was to better understand how test parameters such as drive current or luminance and temperature affect the degradation rate. In addition, this study investigated whether data interpolation could allow for determination of degradation and lifetime, L70, at application conditions based on the degradation rates measured at different operating conditions.
The objective of this study was to understand how optical and thermal performances are impacted in a remote phosphor LED (light-emitting diode) system when the phosphor plate thickness and phosphor concentration change with a fixed amount of a commonly used YAG:Ce phosphor. In the first part of this two-part study, an optical raytracing analysis was carried out to quantify the optical power and the color properties as a function of remote phosphor plate thickness, and a laboratory experiment was conducted to verify the results obtained from the raytracing analysis and also to examine the phosphor temperature variation due to thickness change.