In search of infrared light source for coaxial fiber illumination

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Scarodactyl
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In search of infrared light source for coaxial fiber illumination

#1 Post by Scarodactyl » Wed May 01, 2019 5:13 pm

I know this is an odd question, but I have been helping a friend improve the photomicrographic setup in their lab. I was able to help with the camera and the optics, but they're also looking to improve their illumination. This is where it gets tricky, since they use 830nm near infrared coaxial illumination. Their current illuminator is a 300w oriel unit, which I thought at first look to be using a xenon bulb but apparently uses 300w 24v halogen bulbs instead? Specifically Ushio 1000845s https://bulbster.com/lightbulbs/ushio-j ... -4250.html 
I am not sure if it has been modified to use these bulbs or if that's actually what it is meant to take. 

Their current illuminator has developed some inconsistencies and is not portable, so ideally I'd like to get them something like a standard 150w illuminator. However all the ones I've looked at seem to have significant IR filtering (which makes sense for a cool light source), and I can't find any illuminator (or really anything) that would accept 300w 24v halogen bulbs. Plenty for 150w 24v halogen bulbs, and one that's 250w. 
At the moment I have a few ideas, but I am not sure if any of them are good. The first two in particular are a bit too dangerous for me to feel good about trying without some reassurances. 

The first is to attempt to modify a 150w halogen bulb for a normal 150w fiber illuminator. They have a double-shell construction, with the inner halogen contained within an outer bulb. I wonder if removing the front glass plate will allow IR to pass through, or if it will just make the bulb explode. 

The second is to just put one of the 300w bulbs in a 150w 24v illuminator and see if it catches fire. 

The third is to try and modify a 300w xenon source to take his 300w bulbs instead of what it's supposed to take, but this is definitely not something I'd approach incautiously or comfortably. 

Fourth, I ordered an 830nm LED bulb meant for therapeutic IR usage. I am not sure if it will be particularly possible to couple that to a fiber light guide given that it's a few distinct point sources. Maybe with a diffuser and lens?? 

Or fifth, just tell them to scrape up the cash for something like this from thorlabs. it's 850nm but produces a reasonable amount of 830 too https://www.thorlabs.com/thorproduct.cf ... ber=M850F2 (I am also not sure if this just plugs into a wall or if there's going to be more to do after it's bought). 

Does anyone know how insane the above ideas are, and or if there's a better option?

Hobbyst46
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Re: In search of infrared light source for coaxial fiber illumination

#2 Post by Hobbyst46 » Wed May 01, 2019 6:13 pm

Not a direct answer but just some thinking, without experience in IR microscopy. Admittedly, I refer to the light sources, not to fiber optics or light guides.

Assuming that the wish is an efficient source of about 830nm light. Also assuming that the specimens contain water.
Water absorption of IR radiation rises steeply beyond the visible range (700nm) into the longer wavelengths. A 10micron light warms the specimen much much more than 1 micron does.

So:

1. Xenon or Mercury arc lamps have a peak intensity in the 800-850nm range. The wattage is typically 75-150W. Yet their power supply is electrically different from a halogen power supply. Plus, they also emit in longer wavelengths, roughly >2.5 microns, so they are heat sources. Better use them with an interference cutoff filter, say shortpass of 860-900nm, without loss of intensity at 830nm.

2. A LED sounds great IF the intensity is sufficient. If the purpose is excitation of fluorescence, an intense light is essential.

Rather than modifications of commercial lamps and/or power supplies, or new combinations thereof, I would check the theoretical efficiency of a Xenon/mercury arc lamp with cutoff filter against a LED, and against the halogen.

Hope this helps!
Last edited by Hobbyst46 on Wed May 01, 2019 9:36 pm, edited 1 time in total.
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Scarodactyl
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Re: In search of infrared light source for coaxial fiber illumination

#3 Post by Scarodactyl » Wed May 01, 2019 7:56 pm

Thanks. I should give a few more details just to give a sense of where we're at.
The 300w light source they're using is more than adequate, in that they get plenty of light when using it at lower than maximum brightness and apparently don't have any significant heat problems. It's just super clunky and old, and he'd like to bring the whole apparatus on the road sometime which isn't possible with that illuminator. They're also using a two-filter setup, one bandpass filter installed in the camera and one before the light enters the coaxial illuminator (though I assume that could also be put right in front of the bulb if needed.)

I did bring a 300w xenon light source from home to try with their setup, and it produced almost no IR (in the sense that the 830-filtered camera could look right at the bulb through the front and it looked fairly dim (and that was after removing a thick glass filter in front of the bulb that did significantly cut IR). I have to assume that the bulb itself has an IR-reflective coating. That one is a DayLite XEnon 300, which takes this type of bulb https://www.medbulb.com/products/XBOR30 ... 7D60C.html But I will take some time to look for more options on the xenon front, as I agree that sounds pretty promising. Of course another issue with xenon lights is that, while I can get a light source with bulb for about 150 dollars on a good day, replacement bulbs seem to all start around 600 dollars.

Hobbyst46
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Re: In search of infrared light source for coaxial fiber illumination

#4 Post by Hobbyst46 » Wed May 01, 2019 9:34 pm

Scarodactyl wrote:Thanks. I should give a few more details just to give a sense of where we're at.
The 300w light source they're using is more than adequate, in that they get plenty of light when using it at lower than maximum brightness and apparently don't have any significant heat problems.
Looks like my opinion of the halogen lamp was grossly incorrect - I cited irrelevant data. I take it back, and appologize. Edited in the post.
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MichaelG.
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Re: In search of infrared light source for coaxial fiber illumination

#5 Post by MichaelG. » Wed May 01, 2019 9:37 pm

With all the safety warnings assumed

This may be of interest:
https://www.ebay.co.uk/itm/Module-Laser ... 3501201141

MichaelG.
Too many 'projects'

billbillt
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Re: In search of infrared light source for coaxial fiber illumination

#6 Post by billbillt » Thu May 02, 2019 12:51 am


PeteM
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Re: In search of infrared light source for coaxial fiber illumination

#7 Post by PeteM » Thu May 02, 2019 11:46 am

Probably a lousy solution, but a lot of the old Kodak Carousel slide projectors used a 300 watt halogen bulb - and safely. I'd guess there's an IR filter you'd have to remove and a fiber optic retainer to adapt to a lens shell - a bit of lathe work. They're sort-of portable, neat carrying cases and all . . . They do have the advantage of being dirt cheap used and with a properly engineered power supply and fan for the 300 watt load.

Seems a LED would be the better and modern solution, but a bit more time to cobble together or fairly expensive if someone sells an IR supply like this.

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wporter
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Re: In search of infrared light source for coaxial fiber illumination

#8 Post by wporter » Thu May 02, 2019 2:08 pm

Pete, not a lousy solution at all, in fact, my first thought, too. The Carousels had a heat-absorbing glass disk about 1/4" (6mm) thick, and 2.5" (60mm) diameter, greenish-tinged (that are sold all over ebay as replacements) that can be easily removed: presto, instant IR.

Scarodactyl
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Re: In search of infrared light source for coaxial fiber illumination

#9 Post by Scarodactyl » Thu May 02, 2019 5:19 pm

Thanks, that looks interesting! Someone at photomacrography pointed out an ir-intensove halogen that thorlabs sells, but it does require a more expensicw housing than a regular 150w illuminator so I will look into this as well.

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wporter
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Re: In search of infrared light source for coaxial fiber illumination

#10 Post by wporter » Thu May 02, 2019 6:20 pm

How about something like this, if you can easily remove the IR block:

https://www.ebay.com/itm/Leitz-Microsco ... SwuMFUhs45

Scarodactyl
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Re: In search of infrared light source for coaxial fiber illumination

#11 Post by Scarodactyl » Thu May 02, 2019 7:39 pm

I was considering that one, the only concerm being hookong it up to the fiber optic. But it may not be that difficult after all. If I do give it a go I will be sure to post about kt.

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