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Re-defining Solid State Light Sources (Lindsay Stefans)


Good morning, good afternoon, good evening depending on where you are. I am Lindsay Stefan and I am going to talk to you about Re-defining Solid state light sources. And just to give you a brief background about myself, I am senior product manager at Philips lighting LED systems. My background originally is in architectural lighting design. And I really hold the belief that Lighting is both an art and a science. The art informs the science and the science informs the art. So just a little overview of what we will look at today, we will look at three factors of solid state light sources in the broader context of the history of light source development and I want to emphasize form. So we are really going to look at form and not lighting technology as in overall technology but focusing on the form. And then we will learn how to contribute to the ongoing discussion of the commonality of solid state light source engines and interface specification and we will also gain insight into the direction in which one factor of LED light engines and OLED forces are headed and how that can affect the design process or design parameters.

So just to start and make sure we are on the same page. This is a very safe explanation of lighting sources and unlike incandescent or fluorescent, the solid state sources create light through solid-state electroluminescence. The semiconductor sources. So one of the big differences is conventional sources create light from thermal radiation and solid state sources through solid-state electroluminescence and that is a good event to our discussion as I said not only about the technology and how the light is produced but the form factor.

So conventional light sources, the technology is very much linked to glass technology, vacuum techniques the purification of gasses with solid state lighting is not connected to the glass. That really makes a big difference when we are thinking about form. Here I am going to equate the history of light sources with the history of art. And again this is a very condensed version of the history of art. But you will see on the left there the period of art in a highly condensed form and then on the left there is the general categories of light sources through time and up until modernism there are basically incandescent sources and art sources and what is amazing is that from 400000 BC up until 1802 man just relied on fire for illumination. And then in 1802, which is the neoclassical prime of art that is when Humphrey Davy and Petrov discovered light emission from incandescent wires and electrical arc.

So now we are in the Post-modern era of solid-state light sources. So what does that mean? Post-modernist art typically employs new media and materials and stresses the importance of communication from artist to audience and seeks to renew the big question: ”what is art?” so when we are thinking about light sources I think we can definitely relate to that idea of new media and material solid state light sources certainly invokes that feeling and in terms of communication, the way I look at that is digital network so that really is a part and parcel of solid state light sources or the potential of solid-state light sources. And of course you know, with new technology there is lots of varying qualities and claims and I have put two quotes there: “confusion is the welcome mat at the door of creativity.” And the other quote by Marshall McLuhan: “Our Age of Anxiety is, in great part, the result of trying to do today’s jobs with yesterday’s tools.” Perhaps you can relate to both of these quotes of neither, I just thought it was interesting to kind of put it out there as food for thought when I was thinking about solid state lighting.

Despite the confusion, I think one thing we can agree upon is that our four factors are not limited to glass technology. So that opens this up. So you see on the left there is a photograph of the early Edison lamp of the late 1800 and then all the way to the right you see a flexible OLED source and you see that the form factors indeed have changed but what is also amazing is that still the form factors on the left in many variations of incandescent lighting today is pretty much around so everything is sort of operating now simultaneously from that far left all the way to the right.

So with our first light sources the American national standards Institute or ANSI, they cut a light bulb in terms of specific shapes and I think you can see the coding on the bottom there of the various lamps and that is familiar I am sure to many of you and the photograph there of the man on the right of a man screwing a light bulb I am sure is a very identifiable sort of form that we can relate to and the tangible aspect of light sources. For today I am talking about solid state light sources but I am not really going to focus so much on LED lamps. Not to discount the technology of course there is some amazing advances so in terms of form factor, we can see where the forms came from, so they came from, sort of an anti-standard, so you just saw BR-30 incandescent and there is a BR-30 LED lamp, so it is pretty easy to make that correlation of the form factor so that’s why I am not really going to go into that today.

And just a little story about FC and form factors, in 1904 there was a big fire in the city of Baltimore and just many blocks, building after building caught on fire and the fire departments were called in from New York City and from Washington DC and they all arrived to help out but what happened was, their fire hoses wouldn’t sit in the fire hydrants in Baltimore and they couldn’t help out .That is just an example of some interfaces not being standardized .so there in the photograph you can see, a very, this is a, LED engine, you can see in the middle of the socket.

So this is something that is very much related to that development of the ANSI standard and socket standard. So in terms of these interfaces, an organization called Zhaga which some of you may know about or some of you may not. I am just gonna kinda briefly talk about Zhaga today. So Zhaga is a consortium of 214 companies all around the globe and the mission is to promote the interchangeability of LED light engines. And you may wonder what Zhaga means, it actually is, Zhaga is the name of a waterfall in the Sichuan province. So it is not an anachronism in china. It doesn’t stand for something else. It is just the name of a waterfall in China.

So in terms of LED modules, there are both integrated or separate module-driver combinations and both of these are what we call light engines. But in terms of form it is something as integrated or with a separate control gear from the module, you know you have a very big difference between how you think about the form. And what Zhaga does is they are seeking to find some commonality between these various forms and this is in terms of mechanical and thermal fit, the size of the light emitting surface, the height of the light emitting surface and photometric property.

However, Zhaga does not dictate quality. That is up to the specifier and user, luminaire maker to really gauge what the quality is. So you could think of Zhaga as more of, sort of some of the physical, mechanical characteristics of the LED light source. And for incandescent and or filament sources, sources that always lead with their MOL, maximum Overall Length and LCL, Light Center Length, and that relates to where the filament is in the lamp, which relates to how it interact with the optics and with LED modules we use this term called LES and you may start seeing that more, referred to in various data. So LES is the Light Emitting Surface and that refers to the diameter, of the actual, where the light comes out of the source.

So the 50mm that you see there is the outside diameter of the module and then the yellow part where you see the various diameters, that is the LES and what Zhaga has done is name four categories of LES for a spotlight. There is some variation and they are not all, there is some variation in mm but the idea is that to have this commonality, you can apply similar optic if you change the source. So I think, another thing we can agree upon is that there is really lots of different forms out there today and it is sort of a very open discussion and today I am kinda gonna look at it in two categories looking at solid state sources as either a free form or fixed form and in my belief, there is a place for both.

So my example today of free-form sources are OLEDs and in this photograph, you can see an amazing installation by Jason Bruges with OLEDs and one of the amazing things about OLEDs which really evokes a free form source is how the light is created. So OLEDs, in OLEDs is the organic compound which response to an electrical current and what happens is, a powder is heated up and then evaporated and forms onto the substrate and you can actually almost paint with the light and create masks and put the light where you want it to be. So in the photograph on the right where you see the light. That is where this compound is placed, and where you see the in-between spots, there is actually no light there.

So it is almost in a way that you can think of it as a printing process although you don’t apply the material you would in the printing process. But you can create masks and actually create some thing that is free form. And in the future, we estimate 5 to 8 years from now, OLED will be flexible. So this certainly invokes what I think of as free form. But that being said OLEDs are still a real and viable technology and are being mass produced today. So free form when I think of a free-form solid state light source so many characteristics, you know: spatial freedom, less distinction between the light source and the building material so your light sources …it is hard to make a distinction whether it is the luminaire or whether it’s the source.

So it really kind of opens up the way we think about light sources and alternate ways to sort of seamless materiality. And in terms of fixed forms, we are going to look at today the example of LED modules so in the photograph you see there, there are 8 different sources. They are all 15mm in diameter, but there is a big difference in the types of, the way they are created. There is a variation although they are still within the 15mm form factor. So if you are staying with this fixed form factor you can really focus on development really pinpointing you know color quality or optics by sticking to the same form factor. So one of the interesting things you know, commercialyou think of course is white light sources in color temperature but we are also able now to pinpoint color points on a black body locus with LED light sources. And just to give you a background about the black bodies. So a black body is a theoretical source which will absorb all electromagnetic radiation and as it is heated it moves through various kelvin temperatures.

So in the chart there you could see a black body locus and so as this black body is heated the path is called the black body locus and this can be grasped on a chromaticity diagram so you see the numbers there are 10,000 degrees kelvin all the way over to 1500 then you see the x and the y and those are the color points.so you have these color temperatures graphed on the color points. So the Lighting Research Center, this is also a very brief summary of quite an extensive and interesting study, did a study on white and it was, and the goal was to conduct a lab experiment to investigate the subjective chromaticity of light. So the participants were asked to look at the various white light that had different color points, for example, you could have a white light with 3000k but at different locations on the x-y.

So a different relation on the black body line. And one of the results of this study was that there was a presence of white points from 3500k and lower below, quite below the black body locuscommercials LED light sources, white light sources are targeted quite close to the black body. But what is interesting about this study is that there was a preference for white, below the black body that in between 4100k and 2700k and the whites in this area, they were perceived as having very little tint, so that is kind of interesting to see how that path quite diverges from the black body locus and one of the things we are dealing with in Philips is developing some white light sources that really render white as white. we call it a crisp light but at the same time making the colors pop. So it’s really showing the white, as a, with very little tint, perceived tint, but this is still within the same 50mm form factor.

So, for example, you can have a source that is 3000k, 2000 lumen but a different color point but you can choose, but still in its 50mm form factor so you are really able to dial in and create the different quality of light but still staying with the same form factor. So fixed forms one of the benefits as I mentioned is to really focus the technology and sticking with this single form factor and also replaceability. That is one of the biggest benefits of the fixed form factor. So that in the 1940s and in Richard Kelly some of you already know him, sort of established the principles of illumination he broke them down into three categories: Focal Glow, ambient Luminescence, and play of Brilliants.

So in my belief, whether you are using a free form or fixed form sources, these basic principles don’t change. And these were laid out, these principles and he is sort considered one of the pioneers of architectural lighting design and he was very active at the height of modernist architecture. And as we move now to our post-modernism, of course, there are developed form factors we can rarely expand on his vocabulary. So this is to summarize the summary kind of key takeaways of today, I believe that fixed and free-form sources are both relevant. We need both kinds.

One is not better than the other. It depends on the application, the design objectives or requirements. And for free-form sources, of course, there are major technology advances and we can really think of the light source, you know as a material. And the terms of fixed form sources which really follow a certain trajectory in history as we have seen, there is still a lot of relevance because we can really focus the technology but as far as the physics of objects that doesn’t change. So how the light interacts with a certain optic; whether it’s incandescent, fluorescent; with certain physical properties of the light. So in keeping with the fixed form we can really optimize these optics. And one of the last things I would like to say is having a contribution from end users and end designers are very important.There are lots of advances in solid-state light sources.

And the voice of all different people specifically designers is very important to create this new specification of interfaces and such. You can see that I have posted some questions and this time you can feel free to send in some comments and I would read out some of the comments, just thoughts, and opinions you have. And related to those questions or you can send in a question that you have and I will try to answer it. And some of those questions I posted there if you don’t want to send them over today during this webinar. You could feel free to email me some of you feedback.so Ok….I am looking to see here, just give me a moment.

At some of the questions. Just give me a second. So one of the questions here is: could Zhaga go beyond its current mission of interchangeability and go towards setting comparison standards both in LED and OLED. It seems to be the only bodies that could help to guide and expand the SSL industry to be a driving force with so many members. So Zhaga is definitely, you know, just typically trying to make it easier to have this interchangeability and stable platform for luminaire makers, so their mission is not really to tell you what the quality is.

That is really something they are not going to step into. So that being said, by establishing these stable platforms it does make it easier for people to make comparisons, so although they don’t actually tell you what type of quality it does make it easier for someone to determine the quality. So that was one of the questions and I am looking at one other comment here. Just give me a moment. Ok one of the questions, which I can’t answer but, is : how many people and what background would subjects in the BBL curve white test. So I am going to sort of just direct that question to the Polytechnic institute because they conducted the study, it’s a very interesting study and it was presented with strategies of light. If you want to find out more you can contact them. Let’s see. Some other question here. Well this is another question that I really can’t answer because, let’s see, I think it’s an open. As I said I really believe in both free form and fixed form there is a place for both technologies.

The question here is all those potential is for free form and the ability to become light as part of the architecture, where do you think that leaves traditional luminaire manufacturers. It’s no longer forming luminaires, more of an integration of other technologies and architectural components. So my thinking about OLEDs is you could think about it as source luminaires but I think about it almost as a material in itself, so it sits somewhere in between illumination, display, and even graphics. I don’t think we should limit our view in thinking of OLEDs as something for a luminaire although it can be used in a luminaire. I think we should really think of OLED as expanding areas in other ways of using light.

And let’s see. And that leads to another question I have got. It’s: What are your thoughts on integrating SSL directly into buildings and materials and furnishings and moving away from traditional pictures. So OLEDs one of the things that they can do now is make them transparent when they are off. So this certainly opens up uses that we can think of, you know, in windows, in gracing materials. So I definitely see that trajectory as being very integrated into building materials and furnishings and signage and graphics and such.so let’s see.

So this is just a comment from someone. It’s not a question. It says: unless free form OLED can be standardized to agree fixed form will always be more popular. Most efficient and low-class free form will be the art piece so that was just a comment from someone. Let’s see. So I don’t have any more questions here unless somebody wants to send in some more and as I mentioned feel free to email me if you want to continue the dialogue but otherwise we can sign off as I have no more questions.

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