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#22
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Back to the IR light source concept...
In article ,
(Chris Hodges) wrote: Don Bruder wrote in message ... snip After spending some time looking for, and a grand total of 8 dollars acquiring, a few of these "black" CDs, I went to work on taking my idea from the realm of theory to reality. And I'm pleased to say "it works!" snip So at this point, I'm trying to figure out the best way to polish out the scratches left by the steel wool, and get back to a truly transparent (rather than translucent) finish on my homemade "filter". Have you tried (in other words it probably won't work, but you never know) aplying a water based clear varnish to the ground side. Not an actual "varnish", but the transmission DID seem at least somewhat better during my "pre-testing testing" - before I managed to get all the 40-weight washed off the piece. I was kinda half-considering trying to shellac/varnish/clear-coat the thing in hopes of filling the scratches, but haven't really made a lot of progres on the idea since the initial "feasibility study", due to being handed yet another fistful of "hot irons" to add to my "fire". Another couple of options I've pondered, but haven't really gone anywhere with so far are flame-polishing (before I try that, I'll need to do some playing to figure out if it even *CAN* work for this material) and coats of beeswax (Got plenty of that available, for nothing more than the effort of going out to the hive and pulling a frame...) or perhaps a beeswax/alcohol mix similar to varnish/shellac. This is clearly going to end up being one of those "ongoing project" projects - As I've got time, ambition, and materials, I'll probably tinker with it on and off for the next year or so, until I either get bored, or get it to what I consider "done enough". If the refractive index is similar enough to the plastic (tinted polycarbonate I would guess - normal polycarbonate has n~1.56) and you can get good coverage right into the grooves (you might need to dilute with water) AND you get an even layer it might be good enough - it's light delivery, not imaging that you're after. Underdriving the bulb will increase the amount of IR at the expense of vis as previously mentioned, so perhaps the bulb from a 4 or 6 cell maglite would help as well. Counterintuitive... I don't see an underdriven filament putting off a larger *ABSOLUTE* quantity of IR - Rather, I see the relationship between mount of IR and visible output changing - As in the IR output stays (nearly) the same regardless of voltage, but the visible component falls off with the voltage drop until the point where visible output is nearly nil, but the IR output is just as strong as ever. That's not much different than running a filter - No net increase in absolute brightness, but a relative increase in IR output compared to visible. At some point beyond that (exactly where, I'm not sure, but I *KNOW* that point MUST exist) the IR output is going to start dropping along with the voltage. The "increase IR versus visible output" concept is good. But how does dropping the voltage *INCREASE* the actual IR output? Or is it as I say above - namely, the IR radiation stays (pretty much, and only down to a certain point) the same, but I don't have to "work so hard" to remove the smaller amount of visible light to get near-pure IR? -- Don Bruder - - New Email policy in effect as of Feb. 21, 2004. Short form: I'm trashing EVERY E-mail that doesn't contain a password in the subject unless it comes from a "whitelisted" (pre-approved by me) address. See http://www.sonic.net/~dakidd/main/contact.html for full details. |
#23
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Back to the IR light source concept...
So at this point, I'm trying to figure out the best way to polish out the scratches left by the steel wool, and get back to a truly transparent (rather than translucent) finish on my homemade "filter". Is there a reasonably easy way to do so? I don't know... I went after the thing with 4-0 steel wool - as fine as I know how to locate - under a layer of 40-weight motor oil, and although I did my best to avoid excessive scrubbing (and therefore, scratching) I ended up with a semi-matte, and therefore semi-translucent, finish on the filter. My next move is probably to a 2400-grit wet/dry sandpaper that bills itself as "Mirror-Brite", and to the touch, feels just about as abrasive as a sheet of regular printer paper. From there, my guess is that I'm going to need to move to something like rubbing compound, rottenstone, or even ultra-fine jeweler's rouge. Does this seem reasonable to those who have done optical grinding work? Or am I way off base here? Some modern automobiles use a plastic headlight assembly that 'fogs' with age.. some fog fairly quickly. Inexpensive kits are become available to polish the plastic lenses back to clear.. if the scratches aren't too deep on your lens, this might work for you. Search on fogged headlight lenses... here's one product.. http://www.autodetailingsolutions.co...astic_care.htm Hope this helps.. Jim |
#24
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So at this point, I'm trying to figure out the best way to polish out the scratches left by the steel wool, and get back to a truly transparent (rather than translucent) finish on my homemade "filter". Is there a reasonably easy way to do so? I don't know... I went after the thing with 4-0 steel wool - as fine as I know how to locate - under a layer of 40-weight motor oil, and although I did my best to avoid excessive scrubbing (and therefore, scratching) I ended up with a semi-matte, and therefore semi-translucent, finish on the filter. My next move is probably to a 2400-grit wet/dry sandpaper that bills itself as "Mirror-Brite", and to the touch, feels just about as abrasive as a sheet of regular printer paper. From there, my guess is that I'm going to need to move to something like rubbing compound, rottenstone, or even ultra-fine jeweler's rouge. Does this seem reasonable to those who have done optical grinding work? Or am I way off base here? Some modern automobiles use a plastic headlight assembly that 'fogs' with age.. some fog fairly quickly. Inexpensive kits are become available to polish the plastic lenses back to clear.. if the scratches aren't too deep on your lens, this might work for you. Search on fogged headlight lenses... here's one product.. http://www.autodetailingsolutions.co...astic_care.htm Hope this helps.. Jim |
#25
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Back to the IR light source concept...
Don Bruder wrote in message ...
I don't see an underdriven filament putting off a larger *ABSOLUTE* quantity of IR - Rather, I see the relationship between mount of IR and visible output changing - As in the IR output stays (nearly) the same regardless of voltage, but the visible component falls off with the voltage drop until the point where visible output is nearly nil, but the IR output is just as strong as ever. I'll try and model this and get back to you - but if it's battery driven (i.e. if you really want to use the maglite) it will improve battery life. Chris |
#26
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Don Bruder wrote in message ...
I don't see an underdriven filament putting off a larger *ABSOLUTE* quantity of IR - Rather, I see the relationship between mount of IR and visible output changing - As in the IR output stays (nearly) the same regardless of voltage, but the visible component falls off with the voltage drop until the point where visible output is nearly nil, but the IR output is just as strong as ever. I'll try and model this and get back to you - but if it's battery driven (i.e. if you really want to use the maglite) it will improve battery life. Chris |
#27
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Back to the IR light source concept...
On Sat, 31 Jul 2004 20:43:22 GMT, Don Bruder wrote:
Now to refine the idea... Although the "filter" I built is functional, it seems to be doing a bit too good of a job in scattering the light - Almost certainly due to the fact that my method of removing the reflective material from the base plastic of the CD left what's probably best described as a crude "ground glass" finish on it - Instead of being the usual pristine "It's so clear, it's like nothing is there at all" plastic, my scrubbing to remove the coating has created a more-or-less matte finish that doesn't transmit anywhere near as well as I had hoped. Kind of like a lens that has somehow escaped from its proper holder, then spent the last few months bouncing around in the bottom of your ditty-bag with all kinds of things that a lens isn't supposed to associate with if it's going to remain unscratched and clear until it has become "frosted" by all the scratches it has acquired. So at this point, I'm trying to figure out the best way to polish out the scratches left by the steel wool, and get back to a truly transparent (rather than translucent) finish on my homemade "filter". Is there a reasonably easy way to do so? I don't know... I went after the thing with 4-0 steel wool - as fine as I know how to locate - under a layer of 40-weight motor oil, and although I did my best to avoid excessive scrubbing (and therefore, scratching) I ended up with a semi-matte, and therefore semi-translucent, finish on the filter. My next move is probably to a 2400-grit wet/dry sandpaper that bills itself as "Mirror-Brite", and to the touch, feels just about as abrasive as a sheet of regular printer paper. From there, my guess is that I'm going to need to move to something like rubbing compound, rottenstone, or even ultra-fine jeweler's rouge. Does this seem reasonable to those who have done optical grinding work? Or am I way off base here? --- You're probably OK, if you want to go through the ritual of never-ending polishing, but there _are_ commercially available polishing compounds out there which might make your life easier. Check out http://www.noscratch.com/novus/index.shtml Or, you might want to go a completely different route and use an acrylic designed specifically for the purpose. Cyro Industries has infrared transmitting acrylic, "ACRYLITE GP" with a color # of 1146-0 which ought to work for you. Check this out: http://cyro.custhelp.com/cgi-bin/cyr..._search_type=3 for spec's. -- John Fields |
#28
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Back to the IR light source concept...
In article ,
(Chris Hodges) wrote: Don Bruder wrote in message ... I don't see an underdriven filament putting off a larger *ABSOLUTE* quantity of IR - Rather, I see the relationship between mount of IR and visible output changing - As in the IR output stays (nearly) the same regardless of voltage, but the visible component falls off with the voltage drop until the point where visible output is nearly nil, but the IR output is just as strong as ever. I'll try and model this and get back to you - but if it's battery driven (i.e. if you really want to use the maglite) it will improve battery life. Well, the whole point of this concept is a portable unit, so battery power is probably the only reasonable way I can go. Nothing says it *HAS* to be a maglight - that was just my "proof of concept" whack at the problem - but it probably will have to be battery powered to make it practical/portable. -- Don Bruder - - New Email policy in effect as of Feb. 21, 2004. Short form: I'm trashing EVERY E-mail that doesn't contain a password in the subject unless it comes from a "whitelisted" (pre-approved by me) address. See http://www.sonic.net/~dakidd/main/contact.html for full details. |
#29
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Back to the IR light source concept...
In article ,
John Fields wrote: Or, you might want to go a completely different route and use an acrylic designed specifically for the purpose. Cyro Industries has infrared transmitting acrylic, "ACRYLITE GP" with a color # of 1146-0 which ought to work for you. Check this out: http://cyro.custhelp.com/cgi-bin/cyr...p?p_sid=rANE2B ih&p_lva=&p_li=&p_page=1&p_prod_lvl1=4&p_prod_lvl2 =6&p_cat_lvl1=%7Eany%7E&p_ca t_lvl2=%7Eany%7E&p_search_text=1146-0&p_new_search=1&p_search_type=3 for spec's. Hmmm... that one has possibilities, though I cringe at the idea of how much $$ it will take to get ahold of the stuff... When looking at IR-transmitting photographic filters, I was routinely spotting prices in the $150-$200/6 inch square range for plastic filters - Which is why I ended up going with a "make-do" chopped out of a black CD-R. Even the gell filters (which are very likely to have *VERY* short working lifespans) to transmit IR were ridiculously priced - a 70MM round was tagged at $89, fergawdsake! My budget (which is mostly imaginary, practically speaking) for this project can't even CONSIDER those kind of prices! And glass? HAH! If I can't afford the "cheap" gells and/or plastic, then I don't even need to consider glass, since that seems to routinely be about 130-200% more expensive than the corresponding plastic filter. Now to see if I can find someplace that will tell me how much this "Acrylite" stuff costs... I note a glaring lack of any reference to pricing for it at the link you posted. Most often, I've found that situation to be a red-flag for "If you need to ask "how much?", it's more than you can afford. Have a nice day, and don't let the door hit you in the arse as you leave." materials. Still, now that I know the stuff exists, I might be able to find someplace that sells it in reasonable quantities, at reasonable prices. More investigation is in order, obviously... -- Don Bruder - - New Email policy in effect as of Feb. 21, 2004. Short form: I'm trashing EVERY E-mail that doesn't contain a password in the subject unless it comes from a "whitelisted" (pre-approved by me) address. See http://www.sonic.net/~dakidd/main/contact.html for full details. |
#30
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Back to the IR light source concept...
Don Bruder wrote in message ...
In article , (Chris Hodges) wrote: Don Bruder wrote in message ... I don't see an underdriven filament putting off a larger *ABSOLUTE* quantity of IR - Rather, I see the relationship between mount of IR and visible output changing - As in the IR output stays (nearly) the same regardless of voltage, but the visible component falls off with the voltage drop until the point where visible output is nearly nil, but the IR output is just as strong as ever. I'll try and model this and get back to you - but if it's battery driven (i.e. if you really want to use the maglite) it will improve battery life. Well, the whole point of this concept is a portable unit, so battery power is probably the only reasonable way I can go. Nothing says it *HAS* to be a maglight - that was just my "proof of concept" whack at the problem - but it probably will have to be battery powered to make it practical/portable. I modelled the blackbody curves in excel, and you're right, by quite a margin - I don't know whether the power requirement or the IR output would fall faster for a given emitter as you drop the temperature (assuming temperature control for convenience) so it might not even save battery life. The maglite could be a good way to go - the focussing output would seem to help, even if you have a diffuser effect from the vis blocking filter. Did you ever try multiple visible gel filters - these tend to be cheap (I seem to remember £10 (~$18)/sq foot), and for a maglite even offcuts would be enough, so even cheaper if you have a friendly theatrical/DJ supplies shop that does stage lighting. e.g. Lee filters (www.leefilters.com) "Blood red 789" transmits only 1% visible in the far red, combine with (e.g.) "Bray blue 722" should do it. I found my old swatch book recently (since the last thread) so I can have a look with a lamp and digital camera later. With anything less than hundreds of watts they'll last forever. Chris |
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