Although the maximum brightness of LEDs has been increasing continuously during the past decade, their luminance is still far from what is required for multiple applications that still rely on the high brightness of discharge lamps. In particular for high brightness applications with limited étendue, e.g. front projection, only very modest luminance values in the beam can be achieved with LEDs compared to systems based on discharge lamps or lasers. With dedicated architectures, phosphor-converted green LEDs for projection may achieve luminance values up to 200-300 Mnit. In this paper we report on the progress made in the development of light engines based on an elongated luminescent concentrator pumped by blue LEDs. This concept has recently been introduced to the market as ColorSpark High Lumen Density LED technology. These sources outperform the maximum brightness of LEDs by multiple factors. In LED front projection, green LEDs are the main limiting factor. With our green modules, we now have achieved peak luminance values of 2 Gnit, enabling LED-based projection systems with over 4000 ANSI lm. Extension of this concept to yellow and red light sources is presented. The light source efficiency has been increased considerably, reaching 45-60 lm/W for green under practical application conditions. The module architecture, beam shaping, and performance characteristics are reviewed, as well as system aspects. The performance increase, spectral range extensions, beam-shaping flexibility, and cost reductions realized with the new module architecture enable a breakthrough in LED-based projection systems and in a wide variety of other high brightness applications.
Although LEDs have been introduced successfully in many general lighting applications during the past decade, high brightness light source applications are still suffering from the limited luminance of LEDs. High power LEDs are generally limited in luminance to ca 100 Mnit (108 lm/m2sr) or less, while dedicated devices for projection may achieve luminance values up to ca 300 Mnit with phosphor converted green. In particular for high luminous flux applications with limited étendue, like in front projection systems, only very modest luminous flux values in the beam can be achieved with LEDs compared to systems based on discharge lamps. In this paper we introduce a light engine concept based on a light converter rod pumped with blue LEDs that breaks through the étendue and brightness limits of LEDs, enabling LED light source luminance values that are more than 4 times higher than what can be achieved with LEDs so far. In LED front projection systems, green LEDs are the main limiting factor. With our green light emitting modules, peak luminance values well above 1.2 Gnit have been achieved, enabling doubling of the screen brightness of LED based DLP projection systems, and even more when this technology is applied to other colors as well. This light source concept, introduced as the ColorSpark High Lumen Density (HLD) LED technology, enables a breakthrough in the performance of LED-based light engines not only for projection, where >2700 ANSI lm was demonstrated, but for a wide variety of high brightness applications.
Finding an energy efficient replacement of incandescent candle lamp has been a technical challenge. Compact
fluorescent lamps, for example, can be miniaturized to fit the form factor of a candle lamp but they fail to reproduce its
"sparkle" effect. Empowered by solid state lighting technology along with original optical design, Philips has
successfully developed LED-powered candle lamps "Novallure" with great energy savings (2W power consumption with
lumen output of 55 lumen) and the "butterfly" radiation pattern that mimics the sparkle effect from an incandescent
candle lamp. With new high performance LED packages, novel under-cut prismatic optics and state-of-the-art electronic
driver solution and thermal solution, we have developed a 2nd generation Novallure with breakthrough performance: a
dimmable 2700K 136 lumen LED candle lamp with CRI 90.
On a short to medium term, energy efficient retrofit LED products can offer an attractive solution for traditional lamps
replacement in existing fixtures. To comply with user expectations, LED retrofit lamps should not only have the same
mechanical interface to fit (socket and shape), but also have the similar light effect as the lamps they replace. The
decorative lighting segment shows the best conditions to meet these requirements on short term.
In 2008, Philips Lighting Shanghai started with the development of an LED candle lamp for the replacement of a 15W
Candle shape (B35 E14) incandescent bulb, which is used in e.g. chandeliers. In this decorative application the main
objective is not to generate as much light as possible, but the application requires the lamp to have a comparable look
and, primarily, the same light effect as the incandescent candle lamp. This effect can be described as sparkling light, and
it has to be directed sufficiently downwards (i.e., in the direction of the base of the lamp). These requirements leave very
limited room for optics, electronics, mechanics and thermal design to play with in the small outline of this lamp. The
main voltage AC LED concept is chosen to save the space for driver electronics. However the size of the AC LED is
relatively big, which makes the optical design challenging. Several optical solutions to achieve the required light effect,
to improve the optical efficiency, and to simplify the system are discussed. A novel prismatic lens has been developed
which is capable of transforming the Lambertian light emission from typical high power LEDs into a butter-fly intensity
distribution with the desired sparkling light effect. Thanks to this lens no reflecting chamber is needed, which improves
the optical efficiency up to 70%, while maintaining the compact feature of the original optics. Together with advanced
driver solution and thermal solution, the resulting LED candle lamp operates at 230V, consumes 1.8W, and delivers
about 55 lm at 3000K with the requested radiation pattern and sparkle effect. Some field tests were done with positive