Ring light for microscope

[artag]

I've got a Wild M3Z stereo microscope fitted with a Volpi fibre optic ring light.
It's a great microscope and the ring light is pretty good, but maybe the hot noisy light / fan is past it's best.

I could put an LED MR16 lamp in and maybe feather the fan a bit for lower noise. I've tried a 3.4W MR16 but it's not bright enough. I'm about to try a 7W. I can even still get stock of the original 50W halogen.

But should I lose the fibre optic ring light and get an LED one ? How do they compare ? Most seem to be rather cheaply made but it's an inherently cheaper thing to make. I can probably find a decent quality one if I look far enough.

[Zero999]

An LED replacement halogen light might overheat, although the fan should help and a colleague did replace a halogen in his fibre optic Christmas tree and hasn't had any problems with it.

An LED ring light would be more efficient. Lots of power will be lost in the fibre optic system.

[jfiresto]

The white-ish LED lamp substitutes I have tried, have excited an annoying amount of lateral chromatic aberration, presumably, from their strong peak in the blue. Have you found a LED with a less peaky, broad spectrum?

Do you have an M3Z Type S? I think that model is practically perfect.

[Zero999]

The white-ish LED lamp substitutes I have tried, have excited an annoying amount of lateral chromatic aberration, presumably, from their strong peak in the blue. Have you found a LED with a less peaky, broad spectrum?

Do you have an M3Z Type S? I think that model is practically perfect.

Does it matter for this application? Quite often, colour rendering is unimportant. I don't care about colour rendering, when I'm soldering, or inspecting a PCB.

[jfiresto]

At high magnifications, I see enough Latitudinal CA (yellow and violet fringing) to obscure the edges of shiny solder pads. It is a much bigger issue for a camera which can not sum the left and right images. As the vision is part perception and part imagination, the LCA could be psychosomatic – some are more sensitive to it than others.

[tooki]

The white-ish LED lamp substitutes I have tried, have excited an annoying amount of lateral chromatic aberration, presumably, from their strong peak in the blue. Have you found a LED with a less peaky, broad spectrum?

Do you have an M3Z Type S? I think that model is practically perfect.

Does it matter for this application? Quite often, colour rendering is unimportant. I don't care about colour rendering, when I'm soldering, or inspecting a PCB.

I mean, you literally quoted their explanation of why it matters.

[tooki]

But should I lose the fibre optic ring light and get an LED one ? How do they compare ? Most seem to be rather cheaply made but it's an inherently cheaper thing to make. I can probably find a decent quality one if I look far enough.

I’ve been considering fabricating my own ring light for the microscope at work. Then I can choose high-CRI LEDs.

I’m also considering adding alternate light sources to it: some automatic optical inspection systems deliberately use different colors of light from different angles, so as to effectively capture reflections from different angles at the same time. I dunno if this actually works for human inspection, but it’d be easy enough to try. I definitely want UV (for flux with tracers), too.

[Zero999]

The white-ish LED lamp substitutes I have tried, have excited an annoying amount of lateral chromatic aberration, presumably, from their strong peak in the blue. Have you found a LED with a less peaky, broad spectrum?

Do you have an M3Z Type S? I think that model is practically perfect.

Does it matter for this application? Quite often, colour rendering is unimportant. I don't care about colour rendering, when I'm soldering, or inspecting a PCB.

I mean, you literally quoted their explanation of why it matters.

Please translate it into everyday English. I have no idea what the original poster means by lateral chromatic aberration. It sounds like pseudoscientific jargon to me.

[artag]

The white-ish LED lamp substitutes I have tried, have excited an annoying amount of lateral chromatic aberration, presumably, from their strong peak in the blue. Have you found a LED with a less peaky, broad spectrum?

Do you have an M3Z Type S? I think that model is practically perfect.

I'm maybe seeing a little on pure white paper but I don't notice it on contrasty green PCB material.

The original lamp was a 50W GE MR16 Halogen. I tried a generic 3.7W LED 345 lumen (claimed 35W equivalent though it's subjectively brighter than a 35W Halogen) but it was barely bright enough to use. There is indeed a lot of loss in the fibre.
I've now got a 7W Philips '50W equivalent' at 660 lumens  (I find Philips have a less optimistic view of equivalent than generic manufacturers, and less often disappoint me) and it's way better than the 3.7W.  Despite being a 4000K 'cool white' the spectrum doesn't have any strong lines in blue and the subjectively brightest area in a cheap optical spectroscope is red/yellow..
I have an Osram halogen lamp on the way so I'll be able to compare it more directly (since I can't try the old lamp any more)

The 'scope is a delight to use. It came from a British Aerospace auction. I wish I had a camera tube for it but the cost is beyond my need. I don't know if it's a type S, nor what the difference is, but I assume not since the marking is just WILD M3Z. It's fitted with a 0.5 barlow.

The only drawback is a moderately fussy need for eye alignment. I have both standard and long eye-relief eyepieces but prefer the image without spectacles, partly because I can keep better alignment.

I will continue to experiment with alternate lamps but really I'm interested in whether the LED rings are overall better or worse than fibre optics. I would assume worse because of the smaller number of point sources but I do use it already at maximum lamp iris opening so additional brightness would sometimes be helpful (especially if I were to find a beamsplitter). I'm not too worried about efficiency, any LED runs far cooler than the original halogen.

[tooki]

Please translate it into everyday English. I have no idea what the original poster means by lateral chromatic aberration. It sounds like pseudoscientific jargon to me.

Answer 1: color fringing (most commonly as fringing that is blue-purple facing the outside of the image, green towards the inside), increasing towards the edge of the image. Caused by the fact that refractive materials do not refract all wavelengths equally, causing a prism effect. Good digital cameras (DSLR/mirrorless/phones) are quite adept at fixing this, so we don’t see it as much as in the film days or on cheaper digital cameras — or in optical microscopes.
Answer 2: Just because you don’t know a word doesn’t mean it’s “pseudoscientific”. Your ignorance (=lack of knowledge, no further connotation) is something you could have remedied with a simple google search, rather than replying with the patronizing answer you wrote.

[artag]

Please translate it into everyday English. I have no idea what the original poster means by lateral chromatic aberration. It sounds like pseudoscientific jargon to me.

That wasn't me (the OP) but chromatic aberration is important in any optical application. It's not jargon, its the technically correct term and ensures good understanding.

If you look it up you will find that it's due to the different refractive index of glass or plastic for different colours of light. It's more costly to make a lens that reduces it so it's common in cheap optics as you might find in a consumer lamp or cheap lens. It results in colour fringes, particularly blue and yellow, at the edges of an image, but in the context of a fibre-optic illuminator is likely to result in different colours of light from different directions, casting the coloured shadows mentioned.

[thm_w]

I will continue to experiment with alternate lamps but really I'm interested in whether the LED rings are overall better or worse than fibre optics. I would assume worse because of the smaller number of point sources but I do use it already at maximum lamp iris opening so additional brightness would sometimes be helpful (especially if I were to find a beamsplitter). I'm not too worried about efficiency, any LED runs far cooler than the original halogen.

LED ring is inherently going to be lower peak brightness because you don't want a massive fan and heatsink on the end of the microscope. Thats the advantage of the fiber optics, you take the weight/noise/heat somewhere else. But of course its not cheap, even just for the fiber parts.
You could look at replacement LED automotive bulbs, they are insanely powerful, though I don't know how good spectrum is.

I’ve been considering fabricating my own ring light for the microscope at work. Then I can choose high-CRI LEDs.

I’m also considering adding alternate light sources to it: some automatic optical inspection systems deliberately use different colors of light from different angles, so as to effectively capture reflections from different angles at the same time. I dunno if this actually works for human inspection, but it’d be easy enough to try. I definitely want UV (for flux with tracers), too.

Yes, I did with 95 CRI LEDs (the idea and LED were from SDGs video here), six selectable angles. Works reasonably well.
Its just the one color though, 4000k, no mixed wavelengths. I do UV inspection without magnification, but that is a great idea to have both if magnification is needed.
How powerful do you need?

[artag]

LED ring is inherently going to be lower peak brightness because you don't want a massive fan and heatsink on the end of the microscope. Thats the advantage of the fiber optics, you take the weight/noise/heat somewhere else. But of course its not cheap, even just for the fiber parts.
You could look at replacement LED automotive bulbs, they are insanely powerful, though I don't know how good spectrum is.

I already have the fibre optic, so perhaps the best bet is to replace the halogen bulb but to go beyond what's commonly available in the MR16 package. Automotive is something I hadn't thought of, and there's also the high power COB devices.

[jfiresto]

I happen to be working on pretty much that project – substituting a 9mm optical source COB LED for an MR16 bulb inside a 150W halogen light source.

The original bulb has a 32mm focal point. Focusing the LED's 120° beam to place most of its light on the fiber optic receiver is taking many times that distance. I am trying/using, LED to fiber optic receiver: a Total Internal Reflection (TIR) lens, a convex condensing lens, and a mirror to win distance, as I can't shoot all that in a straight line and stay within the enclosure.

[thm_w]

The original bulb has a 32mm focal point. Focusing the LED's 120° beam to place most of its light on the fiber optic receiver is taking many times that distance. I am trying/using, LED to fiber optic receiver: a Total Internal Reflection (TIR) lens, a convex condensing lens, and a mirror to win distance, as I can't shoot all that in a straight line and stay within the enclosure.

Wonder if it would be possible to use just the original fiber inlet instead, which should be <10mm. Or use a light source that is 20-30mm (round COB)?

https://www.digikey.ca/en/products/detail/samsung-semiconductor-inc/SPHWHAHDNK27YZT3DB/12144710
https://www.digikey.ca/en/products/detail/bridgelux/BXRC-40G10K0-D-73-SE/6557097

[jfiresto]

That may be the way to go. My hope is not to do that as I would like to keep the lens and filter you can presently insert between the lamp and inlet.