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<p>> I have to say that I was very interested in responding to your first email, as I am looking for ways to eliminate the use of mercury arc lamps to LEDs....</p>
<p>I could work on that problem as well. It's a worthy cause, on more than one front. </p>
<p>In general terms, I am currently working on a range of scientific applications of advanced LED technology. I thought illumination of lithography environments (the rooms), critical as it is, is a perfect fit for this focus. You have identified another area that would warrant attention.</p>
<p>I'm happy to look into it and do the necessary research and prototyping. All I need is specifications. If anyone can help with that I'll take it from there.</p>
<p>Thank you,</p>
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<p>-Martin</p>
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<p id="reply-intro">On 2020-02-23 04:37, Mario Portillo wrote:</p>
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<div>I have to say that I was very interested in responding to your first email, as I am looking for ways to eliminate the use of mercury arc lamps to LEDs....
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<div>Anybody out there with the same thought let me know,</div>
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<div>Regards <br /><br /><br /><a href="https://yho.com/footer0" target="_blank" rel="noopener noreferrer">Sent from Yahoo Mail for iPhone</a><br />
<div>Mario Portillo, hbtusainc@yahoo.com</div>
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<p class="v1yahoo-quoted-begin" style="font-size: 15px; color: #715ffa; padding-top: 15px; margin-top: 0;">On Sunday, February 23, 2020, 11:40 AM, martin@algoshift.com wrote:</p>
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<div dir="ltr">Based on a couple of responses it looks like I did a confusing job of <br clear="none" />explaining what I am working on.<br clear="none" /><br clear="none" />I am focusing on lights to illuminate the lab, the room, not to cure <br clear="none" />PMMA. So, yes, this is about lights on the ceiling.<br clear="none" /><br clear="none" />Also, I said "above 500 nm" when I was thinking frequency. I should <br clear="none" />have said "below 500 nm". The point is, as I understand it today, the <br clear="none" />goal is to not have much energy in the blue and UV range of emissions.<br clear="none" /><br clear="none" />Sorry for the confusion.<br clear="none" /><br clear="none" />Thanks,<br clear="none" /><br clear="none" />-Martin<br clear="none" /><br clear="none" />---<br clear="none" /><br clear="none" /><br clear="none" />On 2020-02-21 23:55, <a href="mailto:martin@algoshift.com" rel="noreferrer" shape="rect">martin@algoshift.com</a> wrote:<br clear="none" />> I am currently working on the development of LED-based lights for<br clear="none" />> lithography applications. I came across this list and was kindly<br clear="none" />> allowed to join.<br clear="none" />> <br clear="none" />> I have a background in high-performance, high accuracy LED-based<br clear="none" />> applications going back some twenty years. In addition to that I<br clear="none" />> worked in aerospace engineering, robotics and other work I can't talk<br clear="none" />> about (most recently, SpaceX).<br clear="none" />> <br clear="none" />> At this stage in my new mission I am trying to confirm what I have<br clear="none" />> learned in order to start developing a few prototypes for testing.<br clear="none" />> This is what I know and don't know so far:<br clear="none" />> <br clear="none" />> - Energy above 500 nm should be below 0.001%<br clear="none" />> - Operator metamerism doesn't seem to be much of a concern in these<br clear="none" />> environments (?)<br clear="none" />> - Outgassing is not desirable (I don't have any kind of a<br clear="none" />> specification for this)<br clear="none" />> - No specification on acceptable flicker<br clear="none" />> - No specification on required efficiency (Lumen/Watt)<br clear="none" />> - No specification on the amount of light required, either:<br clear="none" />> - Illuminance (intensity of light on a surface, lux) or,<br clear="none" />> - Luminance (light energy emitted, lumens)<br clear="none" />> <br clear="none" />> Frankly, there really isn't very much data out there. It also seems<br clear="none" />> that semiconductor companies keep their lithography illumination<br clear="none" />> requirements somewhat close to the vest. At least this is what I've<br clear="none" />> come across. I wonder if this is because these kinds of<br clear="none" />> specifications might reveal process details? Don't know.<br clear="none" />> <br clear="none" />> The three main trades I have in front of me at the moment for this <br clear="none" />> design are:<br clear="none" />> <br clear="none" />> - White LEDs with carefully selected film or coating-based filter to<br clear="none" />> cut blue + UV<br clear="none" />> - Green and Red LEDs only, no blue; filtration is still needed<br clear="none" />> - A combination of carefully selected white LEDs with low spectral<br clear="none" />> power above 500 nm along with, perhaps, green and red to enhance;<br clear="none" />> filtration still needed<br clear="none" />> <br clear="none" />> To clarify, the Green+Red LED option still requires filtration because<br clear="none" />> green LEDs produce some energy above 500 nm. If I am to take the<br clear="none" />> 0.001% specification to be true, an optical filter would still be<br clear="none" />> required.<br clear="none" />> <br clear="none" />> White LED's, which, of course, are nothing more than blue LEDs with a<br clear="none" />> phosphor coating are the most readily available high efficiency units<br clear="none" />> in the market. Frankly, if high light output at the lowest possible<br clear="none" />> cost is a requirement it is hard to beat them with a combination of<br clear="none" />> red and green LEDs. That said, depending on how they are selected, a<br clear="none" />> significant portion of the spectral power they emit will have to be<br clear="none" />> converted into heat at a filter or bad things will happen in the lab.<br clear="none" />> <br clear="none" />> The third option involves selecting very warm white LEDs that have<br clear="none" />> almost no blue spike. This means less heating of the filter element<br clear="none" />> and, likely, longer life. This could be an interesting solution.<br clear="none" />> <br clear="none" />> Plastic film based filters degrade over time, particularly if there's<br clear="none" />> a lot of heating due to having too much energy in the undesirable<br clear="none" />> portion of the spectrum. This is where thin film deposition<br clear="none" />> (sputtering?) could exhibit far more favorable band-pass<br clear="none" />> characteristics as long a longevity. Cost, of course, could be an<br clear="none" />> issue.<br clear="none" />> <br clear="none" />> I am very familiar with material out-gassing issues in the context of<br clear="none" />> aerospace applications. Not so for lab usage. Understanding where<br clear="none" />> these limits might lie would be very useful. The perfectionist in me<br clear="none" />> wants to design a T5-class 4 ft LED light fully encased and<br clear="none" />> appropriately sealed in a durable glass tube that is both internally<br clear="none" />> and externally coated to not pass light above 500 nm. At the same<br clear="none" />> time, I do understand that a real solution has to fit a budget as well<br clear="none" />> as technical specifications. Not sure where that intersection lies<br clear="none" />> but I am aware of it.<br clear="none" />> <br clear="none" />> I introduced a term above that might not be familiar to everyone here;<br clear="none" />> observer metamerism. This is a by-product of the spectral power<br clear="none" />> distributions of light, reflection and the human vision system<br clear="none" />> interacting in such a way that two colors that are different might<br clear="none" />> appear the same (or, in general, you have trouble discerning colors<br clear="none" />> that are easy to see under different conditions). If you've ever<br clear="none" />> tried to determine if a steak is well done under a typical white LED<br clear="none" />> light and could not, that's observer metamerism. Mitigation requires<br clear="none" />> "filling in" the emitted spectra in areas relevant to the task at<br clear="none" />> hand.<br clear="none" />> <br clear="none" />> This is why I asked myself this question in the red+green LED case.<br clear="none" />> Both of these have narrow emission spectra. Our brains can function<br clear="none" />> with this kind of light and, yes, we will see it as yellow. However,<br clear="none" />> any colors in the portion of the visible spectrum lacking energy will<br clear="none" />> become challenging to deal with. It's like being color blind. Given<br clear="none" />> that lithography labs are already built to work with yellow light, I<br clear="none" />> find myself wondering how much of a problem, if any, might be posed by<br clear="none" />> observer metamerism in the case of the proposed red+green LED<br clear="none" />> solution.<br clear="none" />> <br clear="none" />> I think that's the basics at this point. I would appreciate any and<br clear="none" />> all feedback, questions and even a good shove in the right direction.<br clear="none" />> <br clear="none" />> Thank you,<br clear="none" />> <br clear="none" />> Martin Euredjian<br clear="none" />> AlgoShift, LLC<br clear="none" />> Los Angeles, CA<br clear="none" />> 661-305-9320<br clear="none" />> <br clear="none" />> _______________________________________________<br clear="none" />> labnetwork mailing list<br clear="none" />> <a href="mailto:labnetwork@mtl.mit.edu" rel="noreferrer" shape="rect">labnetwork@mtl.mit.edu</a><br clear="none" />> <a href="https://mtl.mit.edu/mailman/listinfo.cgi/labnetwork" target="_blank" rel="noopener noreferrer" shape="rect">https://mtl.mit.edu/mailman/listinfo.cgi/labnetwork</a>
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