Epi-Illumination

[colinbm]

Are there any Epi-Illumination systems that work with M42 x1mm pitch extension tubes please ?

[dabateman]

Colin I am not sure I understand the question. 

I have seen epi lumination systems look like this on an optical bench: 

 

 

but you may want to build something simple like this:

https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=8565

[colinbm]

Yes @dabateman like the Thorlabs diagram, inside the 100mm x M42 x 1mm pitch extension tube, between the camera & objective with a 45deg glass mirror.
I have seen a plain glass reflect 45deg to make a through the lens light, but I want it in the M42 tube.
 

[colinbm]

This is the heavy & stable set-up for microscope objectives, the 60x objective has about 6mm working distance.
I an just able to get light in there with the small ring light shown on the objective.
It is working OK & is OK for stacking as the focus moves across the screen.
The periphery of the frame has the best details, but the centre of the image, the light is nearly parallel, so the hollows in the centre lack lighting.
The camera can be fixed in position at focus.
The x & y axis have 0.01mm adjustment & the z axis has 0.001mm adjustment.

[dabateman]

Looking at the cost of components from thorlabs, you might be better off buying a used epi microscope off eBay that takes your objectives or one that includes better objectives. 

 

Unless you want to cut, align and weld it together yourself.  Then you just need the dichoic mirror. 

 

The optical bench setups are open air, no tubes. The diagram I posted above is looking down on the table. The O1 at the far left is the objective in a motorized stage, and the light path flows out of it. Thus the sample sits above, the objective is below the sample (like an inverted microscope)  and the light path flows out to the camera on the bench. The dichoic mirror is labeled DM1.

You could also build an open system like that

 

[colinbm]

Thanks Dave, plenty of food for thought.

[ulf]

I do not think it is possible to do an internal EPI illumination with your 60X objective.

It might be marginally possible, but then you will screw up the image quality, possibly completely, by placing something in the extension tube.

 

In a system with infinity corrected objectives it can be done placing the beam splitter between objective and tube-lens.

There are several systems for that. I have seen structures with Mitutoyo Objectives for industrial imaging.

 

Before the era of infinity-corrected objectives there were special lenses with coaxial illumination and there is a close relative to your 60X with the same optics, but also a circular illumination prism around the imaging optics. They are much wider and are called BD-Objectives.

 

https://www.ebay.com/itm/265448271547

I have one of those with lower magnification and longer working distance where I just blocked off the illumination ring.

 

I think your best alternative is to skip your ring light and try other means of illumination, like a more remote flash and reflectors + diffusors.

I do not think the ring light is optimal

[dabateman]

There are some cheap ebay options like this:

https://www.ebay.com/itm/381594004205?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=yswxetr-THy&sssrc=2349624&ssuid=RxqKLNPYQr-&var=&widget_ver=artemis&media=COPY

 

Or this:

https://www.ebay.com/itm/124837187028?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=xTALaFqJRMC&sssrc=2349624&ssuid=RxqKLNPYQr-&var=&widget_ver=artemis&media=COPY

 

I also noticed that the Omax scope link above says that a kit for 330nm to 385nm illumination can be added. So the optics might be good to that level and the 365nm line might be unblocked from that Mercury bulb. 

 

Just search for Epi microscope and you may find something even new that might fit your desire. 

Do you only want visible illumination or also UV? That might change things, but I did find some of these cheap Chinese microscopes like the Omax pass down to 360nm thought the built in optics.

[dabateman]

Something like this could also work for you: 

https://www.ebay.com/itm/123738241640?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=zwtp2oliRLm&sssrc=2349624&ssuid=RxqKLNPYQr-&var=&widget_ver=artemis&media=COPY

The camera goes on the left port. You can also buy 100x 0.8 NA air objective for these.

 

This link will give you an idea with the c-mount camera attached: 

https://www.ebay.com/itm/163566331837?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=SYcZbIi5Q1q&sssrc=2349624&ssuid=RxqKLNPYQr-&var=&widget_ver=artemis&media=COPY

 

 

[Lou Jost]

I use several epi techniques, none restricted to a particular diameter tube. For microscope objectives, as mentioned by Ulf, it is easy to get an epi-illumnator from ebay and stick it on a microscope. The epi-illuminators come in several styles. Older ones have little lenses above and below the beamsplitter, to make an infinity space. These can be used with finite objectives. Other ones have no lenses and fit between the objective and tube lens, in the "infinity space". You should make sure you get the kind appropriate for your set-up.

 

A fluorescence epi illuminator with filter cubes gives you the ability to photograph fluorescence, an amazing world.

 

Epi lighting can cause lots of flare in your objectives. This can be eliminated by polarizing the light at the source, and adding a cross polarizer at the top of the epi-illuminator. Some objectives are labeled "epi" and have less internal flare.

 

Ulf mentioned a similar style of lighting, BD lighting, which often works with the same illuminators. This requires special objectives with enlarged shrouds channeling light around the objective rather than through it. These objectives are labeled "BD" and are often quite cheap. They give a more 3-d lighting "look", while through-the-objective epi lighting generally looks flat. Epi illuminators often have a push-pull slider that switches the system from through-the-objective epi lighting to around-the-objective lighting.

 

 

 

 

[colinbm]

@ulf, @dabateman, @Lou Jost
Thanks for your great responses.
I am not dissatisfied with what I have now, but I was looking at the alternatives to lighting & this Epi system seems to be 'pie in the sky' unless I buy it with a microscope etc.
I will keep trying to improve the lighting with other lights that I have. I must admit the focus stacking seems to help to even the lighting out a bit.
 

[colinbm]

Thanks everyone, I have taken a long look at the lighting & made some improvements that I am happy with.
Down the join of the Wing Case of the Green Jewel Beetle it is blue iridescent, before becoming completely green.