The demonstration instrument, manufactured by Dialight Corporation and shown at the Rosco booth, was based around a solid-state light engine that generated an extremely high flux density of 1,214 lumens per square inch.
"Ours is a three-dimensional approach, as opposed to using a flat LED array," says Mark Roush, VP of Illumination Futures for Dialight. "We have a patent-pending optical system that allows us to stack the LEDs, and the flux density figure is based on the size of the optical aperture."
The initial products based on this technology include both spot lighting and flood beam projection instruments, which when coupled with frontal secondary optics will provide 6,000 lumens in a 500-watt solid-state LED package. "We've already built a larger prototype device that can illuminate the top of a 22-storey building from the ground," says Roush. Dialight plans to introduce an entire line of lighting instruments that will be distributed by Rosco.
Color mixing
A typical problem with multicolored arrays is that individual pixels can be seen when viewing the source directly. A secondary problem is that when the source is pointed at an object, the shadows have colored edges, a phenomenon known as fringing. "The light from our RGBA (red, green, blue and amber) light engine is mixed before it comes out of the instrument," says Roush. "We were able to demonstrate complicated gobos without color fringing."
[A gobo is a patterned screen placed in the light beam of a spot-light or projector to throw patterns or simple images onto distant surfaces.]
Dialight has developed a color specification protocol known as SpectraMix™, which allows complete control of color mixing of more than one billion colors. SpectraMix references coordinates from industry-standard color by Rosco and provides exact specifiable colors, which are repeatable fixture-to-fixture regardless of the composition of the light engine.
SpectraMix incorporates several feedback mechanisms and algorithms to compensate for the inherent variation of high-brightness LEDs and their color performance over time. The color coordinates remain constant when dimmed, allowing unprecedented color reliability for entertainment venues.
"Rosco provides a palette of colors used throughout the industry," says Roush. "Our LED system is able to call up these colors, providing the shorthand for users to get any color they might want." For more on SpectraMix and Dialight's relationship with Rosco, see Dialight teams with Rosco for precise color control.
Theatrical promise
Roush says that the LDI demonstration shows that LEDs are very promising for dynamic lighting such as theatrical and production lighting. "The lumen density is now getting high enough for use in theatrical instruments, where the light has to be aimed at something, rather than simply emitted," he says. "The industry has to start thinking differently. Color is normally achieved using a white light source with a filter in front of it. If you use a halogen lamp to project a blue scene, you have to cut out at least 85% of the energy."
As well as providing spectacular color-changing effects, the use of LED-based lighting equipment could cut down on the number of truck-sized generators required for a performance, or allow less thick cabling to be used, or reduce the heat load on air conditioning systems. "Most theatrical people care about the effect and will pay whatever it takes," says Roush. "However, in the long run, the use of LEDs will make a difference in terms of the cost and complexity of achieving those effects."
The fixture demonstrated by Dialight looked very similar to an industry-standard ETC source 4 fixture. The back half, which would normally hold an incandescent bulb and a reflector, was replaced with Dialight's LED light engine, while the front half of the system was a standard third-party snout.
Dialight is developing its own secondary optics and expects the instrument to be around 30% smaller as a result. "This will have an impact if you have a truss holding up 100 fixtures," says Roush.
The Dialight demonstration also points the way to more architectural applications for LEDs. "The future of architectural lighting is in the subtleties of being able to provide color in a cost-effective way, and LEDs plug into that future very nicely," says Roush. "The point of LEDs is that cost will come down in the future making them more affordable and widely available."
