AmScope camera c-mount-ing

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mcfluffin
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AmScope camera c-mount-ing

Post by mcfluffin »

I have an AmScope MD1800 that came with two collar adapters. The website (http://store.amscope.com/md1800-ck.html) claimed that the adapters make it compatible with c-mount but I don't see how it fits onto the Olympus U-PMTVC I just got. There were some ridges on the camera that I thought there was a slight chance were related to c-mount since I hadn't work with it before but doesn't seem nearly a match and are probably just small baffles. I see some kits like http://store.amscope.com/ad-c23.html that maybe is what I really need. Does anyone have experience with the AmScope cameras that could point me to how they are intended to be used with c-mount? Thanks!
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Alan Wood
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Post by Alan Wood »

On your MD1800, can you unscrew the square top section from the cylindrical part that slides into the eyepiece tube? That might reveal a female C-mount on the top part.

Alan Wood

mcfluffin
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Post by mcfluffin »

Okay I got a little more brave following your advice and took an allen wrench to it and I understand how its put together a little better now. The main body assembly has the CCD and the tube has whats called the relay lens in the Olympus docs:

Image

I don't need the relay lens and the c-mount is underneath it! (I bought a random NFK lens with the tube..may need switching out but its a start) If things were only that simple
:evil:

New problem. The rings on the camera that held the tube in place get in the way of a ring on the Olympus adapter. I don't really want to machine either of these down if possible. Maybe I should find a small c-mount extension tube / adapter somewhere? It probably only needs a 1/4" more although its hard to tell.
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Alan Wood
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Post by Alan Wood »

If you put an extension tube between the U-PMTVC and the top part of your MD1800, I suspect that you won't be able to focus.

Alan Wood

mcfluffin
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Post by mcfluffin »

Okay so the 10 mm adapter arrived and here are a few tests using a NeoSPplan 5X objective. I didn't try to focus on the same thing in each shot was probably a mistake, but it showed another problem. One of the big reasons I was hoping to do this was to increase the FOV of the camera sensor as I downsample the pictures afterwords before doing large image stitches. A lot of the pixels are wasted and if I could get a larger view area the stitches would presumably be easier and faster. However, it looks like the stock relay lens put into the camera port has better FOV than my NFK 3.3 eyepiece. On your (Alan's) site I see there is a 1.67 which presumably would break this barrier but the 3.3 doesn't cut it as I think I'm about 25 % bigger as is.

I guess for next steps I'll try to see if I can find a lower mag NFK and run some more precise focusing tests to compare the image quality. In short my quick test showed that the 10 mm extender enlarged it a little but looking through the eyepieces I didn't recall any worse image quality. I'm not fully opposed to milling out the camera collar as the relay still screws into the c-mount without it but I'd like to make sure I'm getting something useful first.

Stock relay lens in place of the U-PMTVC and NFK 3.3:
Image

With camera resting on c-mount with NFK 3.3 + U-PMTVC and no extension tube:
Image

With camera with NFK 3.3, U-PMTVC, and 10 mm extension tube:
Image

For the curious the images are a (dirty!) iPhone CPU.
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Charles Krebs
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Post by Charles Krebs »

Not quite sure how you are setting this up on your microscope (a picture or diagram might help) but....

These cameras typically have a 1/2" sensor (actual size ~4.8x6.4mm, diagonal 8mm) and when used on a microscope are generally used with a 0.5X lens, which would record a field number of about 16mm (Fairly close to the view seen through most 10X eyepieces). That 0.5X is likely the lens in the tube you removed. An NFK 3.3X (or even the NFK 1.67X) will be far too "powerful" and you will only record a very small section of what you are seeing through the eyepieces. Those NFKs were designed for larger film/sensor sizes than the camera you have.

mcfluffin
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Post by mcfluffin »

Here are the three permutations. I should have also mentioned that I believe my observation tube as a BH2-TR30.

With stock relay lens:
Image

With the 10 mm extension tube:
Image

Resting directly on the mount unable to screw in:
Image

I just did a quick test and 4.4 mm diameter view through 10X eyepiece and only 2.1 mm width through the camera. The AmScope website claims "Built-in reduction lens provides the same field of view on screen as through eyepieces" but I am not using an AmScope. So I guess the real question is with an Olympus BH2 based microscope, what adapter should I use to maintain a large and stable camera view? Seems like c-mount would be nice but clamping eyepiece type would probably also work. Do you suspect that I have as large of a field of view as I'm going to get and should just accept the pixels as "wasted"?
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Charles Krebs
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Post by Charles Krebs »

Yes, your head is the BH2-TR30.

I am not sure of the (physical ) sensor size of your camera, but it is very likely close to a 1/2" sensor (actual size ~4.8x6.4mm, diagonal 8mm).

I can't tell from the pictures you posted what viewing eyepieces you are using. The most commonly used with that head were the WHK 10X with a field number (FN) of 20mm (This FN value does not refer to the "subject" field! A microscope objective forms a real image at the plane of the eyepiece diaphragm. The field-number of an eyepiece is the diameter of the image circle size that the eyepiece can "see"... the diameter of the eyepiece diaphragm.) Typically you want your camera to record, across the format diagonal, about the same view seen in the eyepieces (i.e. the diameter of the circular field viewed.) If your camera does have the 1/2" sensor mentioned above, you would need a 0.4X magnification to get the exact same FN you see (20mm) across the 8mm sensor format diagonal. (8/0.4 = 20). The lens in the tube that came attached to the camera is almost certainly a 0.5X. If you could use the camera as it came "out of the box", you would record a FN of 16mm in the camera (8/0.5 =16). Since you are seeing a FN of 20mm through the eyepieces this would represent a slight "crop" in the camera of the view seen with the eyepieces.

Your Olympus U-PMTVC has a built in 0.3X magnification. The U-PMTVC is intended to be used together with NFK photo-eyepiece inserted in the trinocular tube. If you use a NFK 3.3X together with the U-PMTVC that would mean that the trinocular tube provides a 0.99 magnification to the camera (3.3 x 0.3 = 0.99).... let's just call it 1X. You would then be recording a FN of only 8mm in the camera. (8/1 = 8 ). This would be a quite significant "crop" from what you see in the eyepieces. If you used an (elusive and very expensive) NFK 1.67X photo-eyepiece with the U-PMTVC you would have a trinocular tube magnification of 0.5X (1.67 x 0.3 = 0.5). This is likely the same as the "stock" camera with the tube attached.

There are a couple of "mechanical" points to consider. There are two different "C" mounts... "C" and CS". They both use the same threads but there is a 5mm difference in the flange to sensor distance.
See this PDF: http://www.ikegami.com/cb/products/pdf/ ... smount.pdf

I do not know which "flavor" the U-PMTVC expects of the attached camera (My guess would be a C-mount with a 17.526mm register distance.... but that's purely a guess on my part). And I also do not know which mount is on your camera once you unscrew the tube that it came with. Whatever they may be, a 10mm extension between the U-PMTVC and the camera is not correct and is probably not desirable. But unless you can get a lower power eyepiece (than the 3.3X NFK) you may find that using the U-PMTVC with a very small camera sensor provides much more magnification in the camera than you want.

The other "mechanical" issue may be the configuration at the top of the BH2-TR30. While the inner tube diameter is a standard (~23mm) microscope eyepiece tube, the top part is much narrower than the top barrel of most eyepieces.... except for the narrow NFK series that were made to be used with this head. This "constrictive" top diameter is just under 29mm, and unless the top of your eyepiece is less than that it will not "seat" all the way down to the inner machined shoulder where it should rest. If you wanted to use the tube/lens that came with your camera this might mean that it can't seat all the way down as it should. If the diameter of the tube (indicated by the yellow arrow below) is not less than about 29mm it will not clear the upper part of the mount (red arrow) and "seat" at the proper distance.
Image

As you have seen, it is indeed possible to get an image in the camera with a wide variety of combinations. But it may be tricky to get the magnification you want if you can't properly use the 0.5X that came with the camera. In addition, while you can "de-focus" the microscope to get the camera in focus this is not a good idea. In doing so you are effectively changing the parameters for which the objective was designed. It may not make too much difference with low-power, low NA objectives, but it can degrade image quality with higher power larger NA objectives. Ideally the microscope eyepieces and camera should be in focus simultaneously (or at least very close!).

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