Fiber Optic Illuminator

[Craig Gerard]

Fiber Optic Illuminator

Is a manual iris for intensity adjustment at a constant color temperature a desirable/useful feature when considering an FO illuminator?

Also what about a filter holder, IR filter and the capacity to use coloured filters, is this also something that should be considered desirable/useful?

'DC Stabilized' can someone explain the advantages of this aspect.

Does anyone with an FO illuminator have these features in their unit and do you find yourself using them in practice?

Any advice or suggestions appreciated.

Craig

[Planapo]

Craig,

Though not that much an issue with digital these days, IMO the iris for control of intensity is still a desirable feature for photography. Otherwise, if the intensity is only controlled electronically, you are always altering the colour temperature simultaneously with the intensity. Whereas with both I first set the colour temperature with the current adjusting knob, and then regulate the intensity with the iris while retaining the colour temperature.

The illuminators I know all have an IR filter to prevent heat damage from the illuminated specimen. (And although there is the IR filter the manual has a warning to keep the exit of the light guides at least 10 cm from heat-sensitive or flammable light-absorbing materials to prevent fire.)

--Betty

[g4lab]

Is a manual iris for intensity adjustment at a constant color temperature a desirable/useful feature when considering an FO illuminator?

As Betty says it may be less important than it used to be. When I bought my first FO illuminator , a Volpi from Switzerland, Volpi was just establishing a US plant in Auburn New York. The swiss guy I talked to said they put choclates under their illuminators at shows. Probably using a good IR absorbing glass for the fibers too.

The main good brands of FO sources are FOSTEC (now Schott Fostec and discontinued but sold in such massive quantities that they are easy to find)
Schott, Dolan-Jenner (who probably invented the industry) and Volpi.

Here in the US I tell people to buy all those except Schott. The reason is that Schott has a pain in the neck high precision collet clamp to hold the fiber guide which will only fit Schott guides. Here in the US FOSTEC guides are much more easily and cheaply found. Furthermore FOSTEC guides are somewhat interchangeable with Volpi and DJ. Dolan Jenner have made most of their illuminators able to take anyone's fiber guides by a system of very reasonably priced adapters.

Also what about a filter holder, IR filter and the capacity to use coloured filters, is this also something that should be considered desirable/useful?

All better FO illuminators have an IR blocking filter. Most of these are an optical grade mica sheet or very thin glass or silica substrate with an IR reflective dielectric coating. In the old days in slide projectors and powerful tungsten microscope illuminators these might be Schott KG series or Akzo heat absorbing glass. The dielectric versions are better if you ever want to use the source for any spectroscopic purpose because the Schott glass has all sorts of spectrum shape which is what gives it its blue green color edge on.

Most fiber optic sources usually came with some kind of daylight filter to use but again this is a remnant of days gone bye bye. I got a set of color filters with that 1977 Volpi and never used them(except the daylight filter). You can always put gels over the output of the guides.


'

DC Stabilized' can someone explain the advantages of this aspect.

DC stablilized is good under the following circumstances and undoubtedly more that I am not aware of.

It is used in machine vision where they want to minimize systematic variance in the images when say running a high speed conveyor inspection imaging system.

It is useful in the field when operating on a generator which may have a variety of instabilities, and also where the local line voltage is not rock solid.

One slightly arcane reason to have a DC regulated source is if you have certain cameras like a three shot RGB camera that takes sequential images with RGB filters on a turret or with an lcd RGB filter. The three images are separated in time so the light intensity needs to be steady (regulated). Finally if you are using a scanning camera back these like to have very DC light sources since they step a line ccd sensor across the image plane. Like the three shot cameras the light level between steps needs to be identical to avoid banding patterns.

Again the FOSTEC is the one to buy. Their DCR illuminator meets the above requirements and the DCR II and III have the added benefit of an international autoswitching input from the AC line. That is the unit I would recommend and most of them have an iris too. (made with stainless steel leaves).

There are two current Schott models that have a color temp readout whch is really a voltage readout converted to color temp because the behaviour of lamps is well known. But still an indirect method of measurement. They do have irises on them but I would like it better if they read out what they actually measure which is volts.

Does anyone with an FO illuminator have these features in their unit and do you find yourself using them in practice?
Any advice or suggestions appreciated.

I have a pretty big pile of FO sources that have come my way over the years. Because of the great variety of FOSTEC and compatible guides I see on fleabay it is the one I recommend to all my gemology buddies who ask me about it. Get a DCR II or III with an iris. You will have the problem licked.

The Schott's from Germany are very high quality but you are going to pay much more for the light guides and they will be harder to find too. But they are made in Chermany and the qualitaet is great.

Dolan Jenner's can be gotten very cheaply on ebay and don't have the joy of ownership of a FOSTEC Schott or Volpi (Swiss qualitaet! though they may be made in USA)

There are a few other brands too like Chiu Technical (Long Island New York) whose illuminator appears in a huge variety of liveries including Nikon and zillions of others.

Stick with one that uses a 15 volt 150 watt lamp (Volpi Schott) or a 20 21 22 volt 150 watt lamp.(FOSTEC) There is a Schott and was once a Dolan Jenner that use a 250 watt bulb. IF you think you need this one its time to start looking at an arc lamp source.

One other useful feature that I have only seen in medical illuminators is the ability to "bite" any fiber guide with a jacobs chuck fiber gripper on the light output. This was pioneered in the Operating room headlight market
by a company called Designs for Vision. More recently (probably patent expiration) I have seen this on some metal halide arc lamps intended for surgical use. It was very easy to convince surgeons that the dinky 150 watt lamp driving their headlights made their penises shrink and the only cure was either a 250 watt metal halide source, a 300 watt MH source or maybe even a 300 watt Xenon source with a Cermax or Welch Allyn bulb the latter two the finest illuminators ever made. They DO kick adze. If you think you might have some shrinkage I can probably help you out.

[Charles Krebs]

Craig,

Like Betty, I like having the iris control. I find it less important when using one FO illuminator as the sole light source. But if you use two illuminators, or use one in combination with other lights then it is often very helpful.

I never use colored filters in the illuminator, but I can see the value, especially if you want to use it to augment daylight or electronic flash. Generally I'll just cover the end of the light guide with a "gel" to provide whatever color modification I want.

I do like having the IR filter in the illuminator. On my illuminator that does not have one, the tip of the light guide (inserted in the illuminator) gets incredibly hot... can't be good for the guide. (I have one guide that gives a "yellowish" light, and I suspect that there may have been some discoloration at the illuminator end caused by the excessive heat).

A voltage stabilized unit should provide very consistent output in terms of color temperature and intensity. If your mains power supply is "stable" this may not make much difference.

[g4lab]

Charles,
You may be correct about that yellow delivering illuminator. But it also may be just that the fibers were made from glass similar to the old timey heat absorbing glass where the blue absorbtion makes the color more yellow.

If you want a bit later when I get some spectroscopy gear set up permanently you can send me the suspect fiber and we can measure its transmission spectrum. Heat absorbing glass usually is formulated with iron which has absorbance peaks at 700 and 900 nanometers. If it is caused by cooked epoxy the spectrum will look different. If the fiber was designed originally for illumination then it is usually designed to sit in the hot focus of a qh lamp. But sometime people get aholt of fibers used for sensing or for other purposes where they were not intended to sit in that planet mercury type environment. Those fibers can cook off.

[Craig Gerard]

Thanks for the responses and detailed info.

I'm carefully reading through the posts.

I've been using a Dolan-Jenner MI-150 which originally came without the IR Filter and Filter Holder (it's an optional accessory). The nosepiece does get extremely hot and this concerns me with regard to my collection of light guides; also this unit does not have an iris.

I priced the optional IR Filter and filter holder for the Dolan-Jenner MI-150 and the cost was prohibitive; so I began to consider buying an alternative unit with the required features - the most important being the IR Filter, mechanical iris and preferably international autoswitching input from the AC line. I have been using an Isolation Transformer with the MI-150.

The DC regulated aspect was something I discovered along the way.

Using gels at the output end of the light guides (with some breathing space) would solve the colour temp/filter requirement.

I am currently considering possible FO Illuminator candidates for purchase and have a couple in my sights.

Craig

[g4lab]

Thanks for the detailed info in your response to my question regarding Fiber Optic Illuminators

You are quite welcome.

I'm looking at a couple of units on eBay (all these sellers will ship to Australia):
390027770188 : Volpi 5000-1 (light adjustment = Crescent shaped diaphragm?) I'm leaning toward this one?

The Crescent Shape diaphragm and variants are often used and for this application are fine. Illumination light guides are very highly scrambled.
It is possible that either a crescent OR a regular iris could cause a minor headache with a particular fiber bundle. But the probability seems equal for either of them.

I took a look at your two auctions. The Volpi looks new and clean and 230volt.

The DCR II does NOT have an iris.

here is an auction for a unit that does:
Ironically I have been doing business with this seller but it was the first with iris that came up on a search today.
Here is the second
Just for amuzement I got 54 returns including the above by searching ebay on the word FOSTEC with no refinements.
I got 18 when I searched Schott Fiber Optic and all of them were actually FOSTEC products. This is consistent with the previous 12 years of experience on fleabay.

110454589009 : FOSTEC /Schott-Fostec DCRII (not sure if this one has an iris or whether it will accept an optional attachment that does have an iris??)

I Like the DCR II and III the best. They have international power. The iris is a second knob on the pullout drawer If you look at the various FOSTECs they are all the same pretty much. Sometimes they have other livery on them. (Chiu is the one most famous for that labeling their Lumina with anyones name who would order five or ten)
I had to buy a DCR One (I do have three shot and scanning backs) and take an iris lamp drawer from a different fostec. It is usually trivial. Though be warned SOME FOSTECs are very difficult to open. Usually you don't need to open them. Even to swap lamp drawers, which unscrew , slide out, and have a molex plug. You essentially cannot go wrong with with a FOSTEC.

Am I on the right track do you think? The IR Filter and adjustable Iris are my initial requirements. Should I ask if these units have the IR and Iris?

All FOSTECS have a high quality IR filter, very thin, dielectric coated. Good cooling too.

I'm still a bit confused about the Schott, Fostec, Schott-Fostec aspect

.

FOSTEC stands for Fiber Optic Specialties. I don't remember the TEC being another company. But they were made here in the USA and then those crafty Germans bought FOSTEC in Auburn New York , fired everybody and sent the machinery to China. I suspect they might have done the same thing with the Schott plant in Germany but haven't seen any Schott Illuminators that say Made in China yet. But labor in Germany is even more expensive than labor in Auburn New York probably thanks to a government that tries to watch out for its workers a little more than ours does. Also I can't see why our Federal Trade Comission allowed the sale.

You've indicated that a Fostec unit is to be preferred over a Schott unit - but what about Schott-Fostec units - Fostec are now FOSTEC /Schott-Fostec and their products are okay? Have I understood this correctly?

FOSTEC/Schott are identical to FOSTEC and equally desireable and useable. They would be newer ones too. Schott units are like all camera and microscope gear from Chermany; Excellent
The reason I recommend the FOSTEC over Schott has nothing to do with optical performance (And it seems mostly that any fiber optic from a reputable manufacturer is similar in performance though I have never felt the need to measure. I would not be surprised if Schott had the best performance in parameters like loss per foot because they are primarily a GLASS company. But FOSTEC was a F/O specialist and probably drew their own fibers.)

All the Schott Kaltlichtquellen (Cold Light Sources) I have seen, had a very
solidly engineered collet, to bite the fiber guide hard enough that if it was a so called obedient fiber(which NONE of them are, get a limp one and position it where you want it by other means) it could support the entire weight of the fiber against the weight of the illuminator. This collet is exclusive to Schott and no one else I have noticed makes fibers that will fit this. So if you have a Schott fiber or illuminator to sell , as I have in the past , you notice that on ebay there are only a tiny fraction of the auctions offering all the different kind of trick doing accessories you might want to have , versus FOSTEC.
Furthermore other manufacturers guides like Volpi and DJ seem to be interchangeable which makes the used market bigger.

I sell a few things to some of my gemmological pals, and one lady from England(residing in the US and a world mover arounder), was presented with the above info, and though I encouraged her to take a FOSTEC, she chose a Schott that I had. I think it has to do with satisfaction of ownership. I can think of no other reason. Like owning a Leica, or Zeiss camera, versus a Kodak.

Either of the aforementioned units would probably serve you well.

[Charles Krebs]

Gene,

Is there a way to "recondition" a fiber optic light guide tip. The "yellowish" guide I mentioned earlier is not a big concern for me... but what if the end were either mechanically damaged or heat damaged. Is there a (DIY or otherwise) method of repairing this?

[Planapo]

Gene,

Those "crafty Chermans" provide a little adapter (Schott Lichtleiter-Adapter P/N 158 320) which allows the use of Volpi, Photonic and COLDvision series light guides of larger diameter with the KL 1500 e/LCD and KL 2500 LCD.

--Betty

[Craig Gerard]

I purchased the Volpi Intralux 5000-1. Light output variable down to zero, using mechanical shades incorporated into intensity adjustment. IR in place. 230 VAC. Takes a 14.9 mm (0.586") diameter ferrule. It might accept guides of larger diameter with an adapter? The unit is new and at that price was annoyingly irresistable even with the addition of shipping cost to Australia.

I also purchased the FOSTEC /Schott-Fostec DCRII. As Gene pointed out, it does not have an iris; but a mechanical iris attachment can be fitted to the unit.

It may seem extravagent to purchase two units; but to find such equipment in Australia at an affordable price is beyond difficult. If I find one of the units to be surplus to my requirements there will be no difficulty reselling locally.

As for heat damaged light guides. I had one experience some time ago. Basically, the light guide in question was expecting what I now understand to be an IR filter that was not present on the FO unit I was using at the time. It burnt a 'crater' into the end of the light guide. I have only encountered this on one occasion. I removed the damaged portion; but no doubt it would need to be polished or whatever the correct term is for it to be of much use.

Craig

[g4lab]

Is there a way to "recondition" a fiber optic light guide tip. The "yellowish" guide I mentioned earlier is not a big concern for me... but what if the end were either mechanically damaged or heat damaged. Is there a (DIY or otherwise) method of repairing this?

There are various methods that they use to assemble these fibers. One involves getting the entire bundle saturated with high temp epoxy and drawing them into what will be the flat end and letting the epoxy cure.
Then the end is trimmed probably with a diamond saw and polished to flatness so that the fibers are flush at the ferrule.

So you should theoretically be able to repolish them by using some abrasive like silicon carbide paper that is coarse enough to grind out the defect in a finite amount of time, and then start going to finer and finer abrasives. You would need to make a puck to hold the end of the fiber perfectly perpendicular to the abrasive surface. These are available easily for communication fiber ends. But not at all for illumination fibers.. You would have to gin something together in your workshop.

I have only tried to repair a fiber optic once. It was a bifurcated , stainless steel jacketed fiber designed for optical proximity detection. The stainless fiber end ferrule had become uncrimped from the stainless coiled jacket and fibers were broken. I had nothing to lose. Let us just say that I also gained nothing. (the fiber came from a junk yard) I got as far as getting the old ferrule off and getting alot of epoxy to hold the fibers together.
But I don't have a diamond saw to cut it with.

It may depend on the nature of the damage and of the fiber bundle. I think some are done without epoxy, using heat to fuse the fibers exactly the right amount.

If you have one that is damaged you don't have much to loose by trying to fix it but unless you are very skillfull and patient (which we already know that Charles is ) It probably will be a waste of time.

If it is some kind of special fiber or illuminator that is very expensive or hard to get , then I would contact the manufacturer and see whether they could be induced to fix it. Also probably a pretty long shot. In the US you might twist some arm at Dolan Jenner in Boston or at Volpi in Auburn New York.
Alternatively there are actually a fair number of repair shops out there that repair medical endoscopes which often have coherent (imaging) bundles. They could do such repairs. And they probably would charge less.
(they are competing with each other for business where there is no opportunity to bribe anyone so they have to compete on quality price and service. What a concept!!

Those "crafty Chermans" provide a little adapter (Schott Lichtleiter-Adapter P/N 158 320) which allows the use of Volpi, Photonic and COLDvision series light guides of larger diameter with the KL 1500 e/LCD and KL 2500 LCD.

I was not aware of that item Betty. I kind of presumed that Schott would not even bother with such a thing because why would anyone want to use a light guide from made by anybody BUT Schott. I have worked for enough German and Swiss companies to know how they think.
Would you happen to know how much that little goodie costs? Also I am not familiar with Photonic and COLDvision. Volpi of course makes very fine gear.

By the way , list members might , if in a hurry, be tempted to buy some of the far east fiber optic illuminators and fiber guides which are sold as bundles on ebay.
I have heard from people who have had unsatisfactory experiences with them. Mostly electrical failures. They may not be ready for primetime yet.

[Planapo]

Would you happen to know how much that little goodie costs?

Not yet Gene, haven't got one myself, seen it in one of our labs some time ago and got curious. Going to mail Schott next week for a quote and will let you know.

--Betty

[Craig Gerard]

Betty,

Did you hear back from Schott in regard to the Schott Lichtleiter-Adapter P/N 158 320 adapter?

The FOSTEC/ Schott-Fostec DCR II arrived today. Listing indicates "came off new equipment that was never used". Yep, this unit is new and in excellent condition.
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0416999970

The Volpi should land tommorrow.

Craig

[Planapo]

Craig,

Oops,:oops: thanks for reminding me!
Forgot about it, and didn't do my "homework". Mail has been sent now and I will report as soon as I get an answer.

Congrats on your good deal.

--Betty

[Craig Gerard]

The Volpi Intralux 5000-1 arrived.

The Volpi is much heavier than the Fostec DCRII and emits less noise when operating (that's important); infact, the Volpi is whisper quiet.

The heat protection filter in both units is very good; but it does have an impact on overall light output (have not tried the chocolate test - yet).

The crescent shaped diaphragm in the Volpi is ingeniously simple. It moves in unison with the light adjustment dial and maintains colour temperature. Imagine a circular plate or disc with with a series of crescents, with each cresent slighter larger than the one proceeding it (somewhat similar to the chambers of a Nautilus shell or the phases of the Moon - from crescent to full).

The filter holder for the Volpi is easily accessed externally.

The Fostec is more accommodating with regard to generic light guide diameters and the entire lamp module can be easily swapped-out.

Craig