Hi there, new to the forum, question, tubes for photomicro

nanoranch · Post by **nanoranch** » Mon Jul 24, 2017 5:11 pm

Hey everyone, new to the forum. Suddenly I have a lot of work that requires microscope imaging.

I have a question that is probably obvious to everyone here.

I have a Nikon 20X 0.4 ELWD 210/0 objective and a bunch of microscope cameras. The thing is, I need to mount the objective with a tube to the camera in very unconventional ways. I would like to mount this objective with a camera to different things. For starters I need to mount it to a moving CNC like machine so that I can see the tip of the machine as it works (it's sort of weird). I can't seem to find 210mm tubes that I can mount the objective to and then one of my C-mount cameras (or one of their eye pieces) to the other end. I need to see at sub 100um ranges with a bit of distance between the objective and the thing it is looking at hence the extra long working distance objective.

So, my main question is about the tubes. Google searches just show me regular standing microscopes but what I really need is a tube for the objective and camera. The camera has side mounts attach to my setup. Is the tube more of a DIY thing or can I buy something?

My second question is about the diameters and threading on objectives. They never seem to be listed. This particular objective seems to have a larger diameter than many of the other objectives and turrets I find around the lab. Is there some kind of common diameters for objectives that I am missing here?

Thanks! I will be lurking the forums a lot I expect.

nanoranch · Post by **nanoranch** » Mon Jul 24, 2017 5:45 pm

zzffnn helped me in another forum. I found the thread size online, it is 26mm for all Nikon BD Plan lenses.

Now I just need to find tube and adapter for the 26mm lens. I was also pointed to this link in case it helps someone else:

http://www.photomacrography.net/forum/v ... hp?t=12147

zzffnn · Post by **zzffnn** » Mon Jul 24, 2017 5:52 pm

Try search M26 to M42 or your tube/lens mount size. This is an example:

http://www.ebay.com/itm/M26-BD-Nikon-Mi ... Ciid%253A1

I don't use bellows, but M42 should be a popular camera lens size.

nanoranch · Post by **nanoranch** » Mon Jul 24, 2017 6:07 pm

Since my cameras are all C-mount style, I could also go M26 to RMS, then RMS to C-Mount, then slap on ~200mm of C-mount extension tube.

I wonder what the cheapest route to go is for tubing. This is all much easier to think about after your helpful reply

zzffnn · Post by **zzffnn** » Mon Jul 24, 2017 6:55 pm

Sometimes M42 extension tubes can be very cheap. Maybe C mount too. Sorry I have no experience there. Search, research and compare is the way to go, if you want to save.

Alan Wood · Post by **Alan Wood** » Tue Jul 25, 2017 2:55 am

C-mount extension tubes do exist, but they are narrow (so might be more prone to light scatter from the walls than 42mm or wider ones), and are usually short (so you would need a lot of them, might be expensive).

Alan Wood

ChrisR · Post by **ChrisR** » Tue Jul 25, 2017 3:35 am

The thread sizes are inthe FAQa too - yes the finite Nikon BDs are 26mm, infinite BDs are 27mm.

Note that you'll get more working room and access for lighting if you remove the outer front barrel from the objective. You will also need to block the light path the objective has, intended for epi-lighting. A rubber O ring is neat.

You might want to add an adjustable iris to the setup, in which case M42 is the most available size, and it should go as close to the objective as possible. This would have an influence on your choice of adapter(s).

You will find nice, expensive tubes at Thorlabs and Edmunds, with options for compatible adapters and other hardware - worth a look.

A couple of 20x BD ELWD pics I prepared earlier. Block the red annulus, though there are two different desiigns...

Ichthyophthirius · Post by **Ichthyophthirius** » Thu Jul 27, 2017 5:09 am

Hi;

Keep in mind that at a distance of 200 mm, the field of view on a normal c-mount camera is small to tiny. The Nikon objective covers fields of 26 mm diagonale; most c-mount sensors have only a few mm diagonale https://en.wikipedia.org/wiki/Image_sensor_format

Most c-mount cameras have a reducing lens in front of the camera to capture a larger field. The quality of these lenses can vary a lot.

Regards, Ichty

Charles Krebs · Post by **Charles Krebs** » Sat Jul 29, 2017 2:04 pm

A few additional thoughts. There is a slightly different thread pitch between Mitutoyo 26mm threads and the Nikon BD 26mm thread of your objective. An adapter made for Mitutoyo may not make a good connection with your Nikon. So when you look for the adapter for the objectives (they are pretty easy to find) I would strongly recommend one where the seller has specifically stated it is for Nikon BD 26mm. (your particular Nikon is M26 x 0.75 mm. Mitutoyo is M26 x 36TPI or, stated in decimal, M26 x 0.706).

You should initially decide if you want to work with T-mount tubes (42mm x 0.75) or M42 tubes (42mm x 1). Adapters and tubes are readily available for both, but because of the difference in thread pitch they are not cross compatible. You can also get either an M42 or T-mount adapter with a male c-mount to complete the connection at the camera end.

Whatever you use you need to check the inside for shiny surfaces... normally you need to do some flocking (best) or matte painting (better than nothing but not great) and/or internal flare diaphragms.

Also keep in mind what Ichthyophthirius mentioned. With the very small sensors in this type of camera you may be surprised at how small an area of the subject is imaged.

At best the camera has a 1/2" sensor (actually probably smaller). A 1/2" sensor measures 6.4 x 4.8mm. So at 20X you will be recording a subject field size of 0.32mm x 0.24mm.

If this is your first foray into 20X be prepared for ludicrously shallow DOF