The Lucigen illuminator

[dedalus]

I have recently adquired a vintage Zeiss Standard 14 that i had to restore to be able to use. It featured a very curious combination of light source and condenser for illumination.

The Lucigen illuminator consists on a lamp holder for a 6V 5W tungsten bulb that you can center tilting the bulb holder, and in the regular condenser holder screws, with an up part showing a gross patterned matte surface and a hemisferic condenser lens just over, and then a blue filter deep inside the tube and a couple of cm up, a milk glass with 8mm diameter that will act as a light source.

To adjust the aparent diameter of the light source in the stage you just move all the package up and down adjusting this way the contrast and to some extent the light intensity. There are two versions of the concept, one for use with a regular condenser holder, and one that is screwed under the stage and you can separate from it by turning a very high pitched screw in the barrel.

When i tried to use it first i found that it was very dim with the original lamp technology. There was a 100x oil objetive included that you could't almost use.
But i found a led lamp that was used for very low end automotive tuning, and had a dicroic acrylic lens with a round 8mm led below. I removed the lens in the led package and situated the led (it was not COB) just below the coarse pattern below the integrated lens, with the blue filter removed. This way the surface of the milk glass was lit totally perfectly uniform and in a nice color temperature.

This solved almost all problems with the original device that used a filament difficult to defocus and had a limited cooling ability also limiting this way also the amount of candle power the bulb could have.
It is a very easy to use illumination, you can observe the slide in any position of it and moving it up and down only affects the contrast, in a very effective way.
The only problem with it is that is very difficult to open and you can't add or remove a filter to it easily.
I'm trying to build masks for it with 3d printing in the form of slugs for dark field and lateral illumination that you put over the milk glass. Testing it seems to work but I need more precision building the slugs that my printer allows.

My thoughts testing this device all rotate about why is not a more widely used system today. The original disadvantage was that was very inefficient using the light of a tungsten lamp, with the lamphouse all black walled and a very narrow angle of the lamp emission used, about 45 estereoradians or something like that.

At least would be useful for low end devices to include instead of a condenser and light source placed in the position the condenser usually fits. It is also fantastic for educational use as it will always work in any position letting you at least focus and you inmediately see what the adjust does to the image, and once you set it, it makes the same thing in all the enlargement levels.

I have found in aliexpress led standalone illuminators that seem to be similar in concept, with a led, a tube and a milk glass that acts as light source and don't seem to be very succesful or integrated in a comercial product to my knowledge.

I would like also to know how the image quality, at least in bright field, compares to a Koehler illumination system, that I don't have on hand, for my Zeiss standard 14, and features two diaphragms, a concave metal mirror and a flat mirror inside a prism as well as a condenser lens group, sometimes with an aditional tilting group for NA change up the condenser below the stage. All lit with a metal lighthouse with ceramic parts for an halogen bulb that features a carefully factory centered filament. Very complicated.

Perhaps it would be only superior, granted the led is powerful enough, in the presence of a filter holder for regular diameter filters and the condenser diaphragm works better for out of field light masking? Why are not systems that feature a milk glass as near to the slide as possible to have a totally defocused light source more widely used today?.

I can't also understand why the original system was so light inefficient and all colored black on the inside, tube and lighthouse when in the output the light would be totally decollimated and, i assume, no artifact would appear if it was all chrome. Various lighting systems for microscopy of different ages seem to have this problem and they got by with highly powerful and heat generating lamps or very convolluted gas discharge devices.

[MichaelG.]

An interesting little article, here:
http://www.microscopy-uk.org.uk/mag/in ... cigen.html

MichaelG.
.
Edit: __ See also
https://www.science-info.net/docs/zeiss ... andard.pdf

[apochronaut]

There were somewhat similar illumination systems made for DF use,, with a low wattage incandesdent bulb embedded inside a DF condenser.

[MichaelG.]

Whilst sorting through some of my “come in handy” boxes today, I discovered that I have a complete Lucigen unit [except for the all-important power lead]
.

Zeiss Lucigen

IMG_9342.jpeg (198.52 KiB) Viewed 253 times

.
MichaelG.

[MichaelG.]

For anyone interested in originality … if only for putting an LED in the correct location … here is a snap of the original bulb

.

OSRAM 6V 5W

IMG_9342.jpeg (305.6 KiB) Viewed 225 times

.
MichaelG.
.
.
Ref. __ https://www.proflamps.com/gb/en/Product ... 302843417/

[Saul]

My DIY version:
https://www.photomacrography.net/forum/ ... 45#p296945

[MichaelG.]

Very interesting device, Saul … thanks for the link

A few words describing its use would be appreciated, as you have evidently progressed beyond what Zeiss had in mind.

MichaelG.