<html xmlns="http://www.w3.org/1999/xhtml" xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office"><head><!--[if gte mso 9]><xml><o:OfficeDocumentSettings><o:AllowPNG/><o:PixelsPerInch>96</o:PixelsPerInch></o:OfficeDocumentSettings></xml><![endif]--></head><body>
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....<div><br></div><div>Anybody out there with the same thought let me know,</div><div><br></div><div>Regards <br><br><br><a href="https://yho.com/footer0">Sent from Yahoo Mail for iPhone</a><br><div>Mario Portillo, hbtusainc@yahoo.com</div><br><p class="yahoo-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><blockquote class="iosymail"><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 shape="rect" ymailto="mailto:martin@algoshift.com" href="mailto:martin@algoshift.com">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 shape="rect" ymailto="mailto:labnetwork@mtl.mit.edu" href="mailto:labnetwork@mtl.mit.edu">labnetwork@mtl.mit.edu</a><br clear="none">> <a shape="rect" href="https://mtl.mit.edu/mailman/listinfo.cgi/labnetwork" target="_blank">https://mtl.mit.edu/mailman/listinfo.cgi/labnetwork</a><div class="yqt0188476470" id="yqtfd94529"><br clear="none"><br clear="none">_______________________________________________<br clear="none">labnetwork mailing list<br clear="none"><a shape="rect" ymailto="mailto:labnetwork@mtl.mit.edu" href="mailto:labnetwork@mtl.mit.edu">labnetwork@mtl.mit.edu</a><br clear="none"><a shape="rect" href="https://mtl.mit.edu/mailman/listinfo.cgi/labnetwork" target="_blank">https://mtl.mit.edu/mailman/listinfo.cgi/labnetwork</a><br clear="none"></div></div><blockquote></blockquote></blockquote></div>
</body></html>