Flashlight as permanent illuminator inside the base of the microscope ?

[Hobbyst46]

The idea of using a flashlight as illuminator for the microscope has flashed more than once on the forum, and seems an attractive inexpensive alternative.
Just before the current corona era I purchased a 120mm by 28mm (widest diameter) rechargeable single-die LED flashlight. It is made of metal, focusable, has a three-mode knob (off, on, blink).
And powerful. An impressive cold white beam. I think that the LED is nominal 3W. See photos below. The black matt surface is placed about 20cm from the lens. Costed around 20$.
I tried it on a Zeiss Standard GFL microscope. This has a collimator socket in the base, and the illuminator is inserted from behind. So, this flashlight can be inserted, not quite into the collimator for Kohler illumination; possibly by some lathe work (inaccessible to me anyway), fitting could be optimized.
Preliminary tests show that the brightness of the FOV is decent, at least in brightfield and phase contrast. However, there are two issues: a small one and a big one.

The small is the location of the USB slot on the flashlight. Close to the front end. The flashlight will have to be removed from the microscope for charging.

The big issue is heat. This small tool is not built for long-term operation. Within about 15 minutes, it becomes hot to the touch. During charging, the flashlight is hot, and the charger is very hot. I did not try to measure temperatures, but do not believe that it will survive an ordinary microscopy session.
The heat issue might appear even if the flashlight is just positioned near the microscope and not inserted into the base like I did.
Hence the question mark at the end of the post title..

[DrPhoxinus]

I appreciate your post. Just this morning I was on eBay and put a number of focusable usb flashlights on my watchlist. Some are down to under $10 and have the usb connector at the end but don’t come with the 3.7 V battery. The heat thing could be serious as they probably weren’t designed to be on very long.

Gerard

[Roldorf]

Best option is a headlight lamp with a battery back on the rear. You can split the up and mount the lamp in the scope and have the battery pack and charger on the bench. You could also run the lamp from a mains adaptor. If you i stall a rheostat in the line to the lamp housing you would be able to vary the brightness. A project for when i return from holiday.

[mrsonchus]

Best option is a headlight lamp with a battery back on the rear. You can split the up and mount the lamp in the scope and have the battery pack and charger on the bench. You could also run the lamp from a mains adaptor. If you i stall a rheostat in the line to the lamp housing you would be able to vary the brightness. A project for when i return from holiday.

Yes, this is what I've done in the past with filament-bulbs replacements, for 6V often motorcycle lamps are good, 12V both motorcyles and cars....

[PeteM]

I've had good luck using LED flashlights to replace old tungsten bulbs in several cases (and posted several times here).

This has been best for older microscopes with tungsten bulbs in cylindrical mounts that insert from the back or side (e.g. Nikon S, Zeiss Standard, etc.) I find a barrel diameter that is just larger or smaller than the old lamp socket and either lathe turn it down or make a bushing so it is a snug sliding fit. I may put a mark or a collar so the flashlight can only be inserted to the point were the LED die matches the previous filament location.

The head is cut off to remove the flared front end and reflector and expose the die. It's useful to inspect the flashlight before to be sure it will still retain the mounted die. LED flashlights also work well for a wide variety of "epi" illuminators (AO, Olympus, Nikon, etc.). An Olympus BHM with BF/DF and DIC runs OK on a bright flashlight and becomes very portable.

The best type uses a Li rechargeable battery and with the brightness controls at the back. Formerly these were 3 position (low, medium, high) flashlights and an annoying strobe position one quickly learns to avoid. Now I have a couple newer flashlights that are dimmable and with a USB charger port at the back. They can be plugged in continuously and seem OK at medium power. I will say that these flashlights are pretty cheap (on the order of $20) and things like switches do go bad - often even at first unboxing. Quality control isn't their best feature at this price point. Ones that work initially, seem to go on to reasonably long lives.

These scopes then become portable for use with our "Micronaut" events. Even on medium power they are brighter than the old tungsten bulbs - and don't heat up A single charge might go about an hour. With spare batteries and a charger, almost indefinite operation is possible.

The absolute highest lumen setting for these is too hot for the flashlights -- it's their marketing point rather than a setting you'd want to use for long periods. But lower settings work fine for long periods and are sufficient for most uses, including phase contrast for pond critters. As far as heat (at medium setting or lower), the flashlights put less heat into the base than the original tungsten bulbs.

Were this for a more modern scope, or for one that a hobbyist used all the time and wanted the absolute most even and color corrected lamp -- a dedicated replacement (either home built for from someone like Retrodiode) begins to make more sense. It could be a great way, though, to cheaply repurpose a scope for travel or field use.

Headlamps are useful as well, but usually need major disassembly to get the die at the right place. I use a pair of them sitting on the base for a dual headed comparison scope and also to convert an old Olympus epi scope to add brightfield that's good up to about 20x (200x).

[PeteM]

Here's a somewhat more complex fit - adapted for a Leica DMLB to make it somewhat portable. I still use the regular 100 watt halogen lamphouse that fits at the back while at home. It was also necessary to have an original lamphuse to replicate the mounting dimensions of the aluminum holder I made up.

The simpler adaptations can likely be done with minimal tools, just finding a suitable flashlight, cutting off the head, and making a sleeve. Here the outer envelope of the flashlight is turned down and an adapter made to fit a Leica DMLB. In this case (it was a "zoom" flashlight) it worked best to leave the lens and reflector in place and shove it in to the wide angle position. So, no need to cut off the head - just turn it down to a cylinder. The aluminum mount and close fit also helps a bit as a heat sink.

This is a bright dimmable LED with the controls and USB port clear of the back of the scope. It's fine for normal viewing and the high mode even provides enough light to take a picture with high power DIC. Just don't want to leave it there for more than a minute or so.

[DrPhoxinus]

Pete,

Thanks. Could you post a links from eBay for likely candidates


Gerard

[PeteM]

Here's the one used in the Leica DMLB conversion above (no longer available):

https://www.amazon.com/gp/product/B07CZ ... UTF8&psc=1

Here's one I've been using more recently:

https://www.amazon.com/Rechargeable-Fla ... op?ie=UTF8

This one has a body diameter of under 25.4mm (1") but a large end diameter of 35.5mm. Unscrew the cap and it's around 32mm. There's enough aluminum to turn it down to maybe 30mm. These work pretty well to light up the Reichert Microstar IV scopes we use in portable mode.

The two of them I've bought work OK. Others (Amazon reviews) have reported them bad out of the box - but from Amazon they're easily returned. My experience is that the control cap is the most common point of failure. All controls and charging are from the rear on this model.

Not the best battery or charger but it keeps the flashlight lit when plugged in. A good charger will actually measure charge and cost maybe another $20:

https://www.amazon.com/Battery-Charger- ... _s_sparkle

Add more for a couple spare batteries.

There are even tiny LED flashlights that can light up the pointers in teaching bridges.

[MicroBob]

I had a couple of these cheap LED flashlights apart and the LED was always mounted on an aluminium disc that was just loosely put into a mount made from flimsy.aluminium parts. This is far away from a solid aluminium cylinder and also no trace of heat transmitting compound. So it has to be expected that either the LED is ran at unhealthy temperatures or the power is low. Despite the catastrophic construction they work well for normal flashlight use. But I wouldn't spend much energy on adapting them to a microscope.

The flashlights already have a collector lens, often of surprisingly good quality. This can interfere with the microscope optics that expects a bulb that delivers an undirected light from a certain size filament.

Bob

[PeteM]

Agreed, Bob, that it's not the solution for one's personal best scope.

However to convert a scope with an old or missing tungsten lamp or to make a scope self-contained for travel or field use -- it's an affordable and fairly quick fix. It's also a quick way to check out something like an Ebay purchase with a missing lamp or bad power supply.

As noted above, "Were this for a more modern scope, or for one that a hobbyist used all the time and wanted the absolute most even and color corrected lamp -- a dedicated replacement (either home built or from someone like Retrodiode) begins to make more sense. It could be a great way, though, to cheaply repurpose a scope for travel or field use." One of the other pluses for us, in setting a number of scopes at tables, is there aren't power cords to trip over.

[MicroBob]

Battery powered microscopes are really nice - even on a desktop the cables are a nuissance. A sign of a promisind flashlight would be that it is dimmable then as the amount of light will be enough for brightfield while there is not much heat generated. What I don't know is how they do the dimmng: PWM? In this case there can be a problem with photography.

I use these flashilghts with single 18650 lithium ion batteries. The batteries from the sources of the lamps are fakes though: You get a hollow cylinder with a tiny battery on leads stuck into it!
A sign of a good 18650 is that it weighs about 50g. The fakes batteries can be part of the power management concept: By their tiny size and resulting inner resistance they limit the current of the LED to a healthy level.

It is possible to build a proper LED flashlight with good cooling within the limits of the heat capacity and convection and radiance of the flashlight body. There are internet forums for the weirdest stuff, even for flashlights and microscopy. The flashlight - guys may be able to point us in the direction towards affordable but competent flashlights.

[Roldorf]

Just ordered this to pull apart and mount in my new microscope which is missing the illumination

ansmann-hd5-led-stirnlampe-batteriebetrieben-40-lm-20-h-5819083-510.jpg (80.21 KiB) Viewed 8293 times

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[Hobbyst46]

Interesting ! please tell us the details when done - lamp wattage, beam color, heat sinks etc. Thanks in advance.

[DonSchaeffer]

This is an interesting possibility. I've been using a lamp with a ill-fitting aluminum foil reflector to narrow the beam onto the stage. It doesn't work that well. I don't have a flashlight bright enough to make any difference. I ordered light conducting cables I hope I can meld with the lamp to push light directly to the subject. They didn't arrive yet.

[Roldorf]

Took delivery of the headlamp this afternoon.
Dismantled an old megaphone for the volume control and an on off switch (Sitting in the garden shed for donkeys years).
Removed the lamp and battery pack from the headlamp.
Dismantled the battery pack and cut a slot in the housing to take the slide volume control.
Cut another slot in the end to take the on off switch.
Rewired the positive battery lead to the on off switch, then from the on off switch to the volume slider, from the slider to the positive wire to the lamp.
Negative return from lamp to the battery pack.

Job done. Tomorrow I will seal the cutouts with epoxy glue to tidy it all up and post some picks, maybe even a video, then install it in the scope. Need to find something to diffuse the light a bit more.



Edit: headlamp cost Euro 10.49

[Roldorf]

datenblatt-868337-ansmann-hd5-led-stirnlampe-batteriebetrieben-40-lm-20-h-5819083-510.jpg (88.25 KiB) Viewed 8205 times

[Hobbyst46]

How will heat be dissipated ?

[Roldorf]

Seems to be very little heat from the head lamp, however the place where the new light is, used to be occupied by a halogen lamp bulb and holder which was still in place. The power supply wasn't so there are lots of ventilation slots in the base.

[Roldorf]

OK here is a video of the modified lamp.

https://youtu.be/gt3U172KOWM

Will post another when the lamp is installed in the scope

[viktor j nilsson]

That video is listed as private, so we can't see it.

[Roldorf]

Thanks I will modify as unlisted

Edit: Did that work?

[viktor j nilsson]

Yes, now it works!

[DrPhoxinus]

I see that there are multiple leds in the lamp.
Have you found candidates for diffusers?
Something frosted? I take it the lamp does not have a focus.

Gerard

[Roldorf]

Hi no, no focus just searching around my not so extensive bits and pieces for a diffuser last thing I tried looked white but was in fact 'PINK' under the light, so the search goes on after I have had some lunch.

[Roldorf]

First images in darkfield 20x