Special thanks to contributor Tony Ritchie for collaborating with us on this article. Tony is responsible for the Atlas lightbox project, as well as the two incredible Atlas cavity macros shown in this article. Tony, a professional gemologist, came to us looking for an affordable LED lightbox design which he could build himself. He consulted us on component selection and circuit design, then ran with it. The results can be seen below.
Prior to the 1990s, visible LEDs came in three colors: dim red, dim yellow and a dim, sickly yellow-green color which was misleadingly marketed as 'green' by an electronics industry in mass denial. A 300mcd red LED was considered a miraculous breakthough, and the color blue was nothing but a laboratory fantasy. This all changed with two particular advances in LED die composition: the development of the high brightness InGaN blue chemistry, and the similarly bright AlInGaP red chemistry. The InGaN spectrum has since been expanded to produce any color from yellow-green to ultraviolet, while AlInGaP is reserved for red, orange and yellow devices. High intensity LEDs are used in virtually all modern electronics, often with little regard for the operator's eyesight.
Since the inception of high flux LED technology, device performance has increased significantly. LEDs are now supplanting large scale commercial and industrial light sources, and are poised to replace all conventional forms of lighting in the next few decades. The brightest LED emitters today are high wattage, high flux blue LEDs coated with a yellow yttrium-aluminum garnet phosphor, which radiates when excited, its output combining with the LED's natural output to produce a high intensity white. Such devices are orders of magnitude more efficient than their incandescent and fluorescent predecessors.
Advances in package optics have brought about truly wide-angle devices, and the ability to approximate the entire visible spectrum at full saturation and brightness has led to the invention of the multi-die RGB LED, a device which can reproduce almost the entire range of visible hues. The incorporation of these abilities into a single device allows light of any intensity and color to be created, programmed and modified in real-time.
At this time, the six significant manufacturers of high flux LEDs are Cree, Lamina, Lumileds (Philips), Nichia, Osram and Seoul Semiconductor. Following in their wake are numerous Chinese manufacturers, churning out clones and outright counterfeits of high grade devices. Among these manufacturers, only Lamina's devices are not widely adopted by the hobby electronics community. The causes for this include device cost, a narrower selection of products, and a lack of widespread marketing on Lamina's part. Lamina targets their products towards architectural and industrial lighting applications, and their devices are not often seen in mass-produced consumer products. Nonetheless, Lamina produces industry-leading devices, with superior brightness, efficacy and construction quality.
Lamina currently produces two RGB light engines: The Atlas RGB+ with six dies, and the Titan RGB+ with 27 dies. The Atlas has the advantage of being a single-cavity device, with superior optical qualities and light density. The Titan's strength lies in overall lumen output, sacrificing the Atlas' convenient star-type configuration and single-cavity optics in favor of a 1000+ lumen seven-cavity array. These two devices are the most powerful single-cavity and single-package RGB LEDs in existence today.
Lamina Atlas NT-43F0-0424 RGB+ light engine. The Atlas is equipped with six dies, two of each color channel, and is capable of producing full-spectrum color.
Lamina Atlas RGB+, die cavity at high magnification. Click to enlarge.
Atlas RGB+ light engine, powered to sub-minimal drive currents. At nominal drive current, the Atlas produces 250 lumens, and can be overdriven as high as 300 lumens. Note the unusual spiral and s-shaped die traces, a signature Lamina characteristic. Click to enlarge.
Lamina Atlas NT-42D1-0425 Warm White and NT-42D0-0426 Daylight White light engines. These devices are very similar to a Luxeon V emitter in terms of brightness and efficiency. Lamina has also started producing single-color Atlas devices, in red, green, blue and amber, as well as an 'Atlas II' warm white device with improved lumen output.
We have constructed two devices using Lamina RGB light engines. The first project is a lightbox designed for taking high quality photographs of gemstones and other small objects. This lightbox is a 30cm cube built from white HDPE panels, with four Atlas light engines mounted through holes cut in the top panel. The Atlases are wired in a simple parallel configuration, with each color channel on a separate 1000mA LuxDrive BuckPuck. Each Atlas receives 100-250mA per channel depending on trim settings, well below their maximum drive current.
External view of the Atlas lightbox. Each Atlas is being driven at 100mA per channel.
Manual color cycling using PWM brightness control, 100mA per channel per Atlas. Note that the stone is actually peridot, a vitreous green mineral.
The lightbox installation uses Atlas devices pre-attached to Lamina EZ-Connect socket boards. The heatsinks were salvaged from several old PC motherboards.
Four Atlas assemblies are mounted through holes in the HDPE lid panel.
The mostly completed lightbox.
This is an unaltered photograph of a synthetic gem-grade YAG crystal being irradiated by the lightbox's blue channel. This is the same phenomenon which is used to produce white LEDs.
In addition to the Atlas lightbox, we have also constructed a laboratory light source using a single Lamina Titan RGB+, similar to four Atlases in one large emitter array. The Titan is being driven by three 1000ma BuckPucks, identical to the type being used in the Atlas lightbox shown above. Unlike the lightbox, this device uses a LuxDrive 4016 QuadPuck controller, which features a DMX interface and various diagnostic modes. At nominal drive current, the Titan RGB+ produces approximately 900 lumens of composite white.
Lamina Titan RGB+ light engine, powered to 400ma per channel.
The Titan RGB+ is equipped with 27 dies arranged into seven cavities. The die structure appears identical to that of the Atlas RGB+.
LuxDrive 4016 QuadPuck four-channel driver board, equipped with four 1000ma BuckPuck drivers, only three of which are used to drive the Titan RGB+.
Titan RGB+, blue channel only, driven at 1000ma.
Titan RGB+, RGB composite white, 400ma per channel.
Titan RGB+, cast on a wall using a large projector lens.
It should be noted that the specifications of Lamina Atlas and Titan devices are not static. All variants of Atlas and Titan have seen an increase in brightness each year since their initial release. The table below illustrates the incremental improvements in the Atlas series.
5/19/2006 (Lamina logo in gold with teal outlines on PCB):
Atlas RGB Type 1 - 18.94 lm/W, 11.20% blue
Atlas Daylight White Type 1 - 33.21 lm/W
Atlas Warm White Type 1 - 22.77 lm/W
2/14/2007 (Lamina logo in gold with black outlines on PCB):
Atlas RGB Type 2 - 24.79 lm/W (+30.89%), 10.80% blue
Atlas Daylight White Type 2 - 39.62 lm/W (+19.30%)
Atlas Warm White Type 2 - 24.33 lm/W (+6.85%)
5/21/2008 (Lamina logo in black with green outlines on PCB):
Atlas RGB Type 3 - 29.15 lm/W (+17.59%), 14.01% blue
Atlas Daylight White Type 3 - 46.03 lm/W (+16.18%)
Atlas Warm White Type 3 - 29.43 lm/W (+20.96%)
Atlas Warm White Type 4 (Atlas II) - 46.03 lm/W (+56.41%)
