I’m trying to help out some of my labmates build a single-purpose microscope, with camera, on the cheap. Actually we want a set of four or five in the end, which makes cost more of an issue. If it wasn’t, we’d just buy a bunch of these, but at $6k each (without the camera) that gets pricey.
Here’s the details: We want to record several hour videos of a flat 4 x 6 mm object. For a camera, we think that something like this will serve our purpose nicely. Unfortunately, we’re all rather lost when it comes to optics. All we need is something with fixed magnification.
Conveniently, the object we want to take videos is about the same size as most image sensors. So as I understand it, we just want a lens with a focal length approximately equal to how much clearance we want between the lens and the object we’re observing (ETA: and no magnification in this case. Please correct my ignorance here). As far as I can see, however, all of the lenses I’ve looked at so far have a “minimum observable distance” that’s several times larger than the focal length. This includes macro lenses. What should I be looking for in a lens?
That would be true for a “thin lens” approximation, with a single lens. In reality, if you try to use a single lens, the aberrations would be horrible. It would also be very difficult to use, as the working distance would be really small. This approximation doesn’t really hold true for commercial macro lenses that use several lens groups to achieve longer working distances.
The camera you referred to has a C-mount, which make it easy. There are many lenses available designed for product inspection and the like. Just look for a lens with magnification of 1.0x. Here’s one example:
(Since you are looking at $1000+ cameras, I assume a $745 lens is in the right ballpark?)
I think most lenses in this category (including the one above) are telecentric lenses, which may be desirable for your purpose. It means the magnification does not change depending on distance from lens to object.
p.s. On second thought, you may want a better lens than I linked to. That lens only claims 40% contrast (I think) at 40 lp/mm resolution. Your camera has 4.65um pixels (equiv. to 215 lp/mm).
You should try a still camera “macro” lens; they are designed to work well at ratios up to 1:1. If you need to go to a little higher than same size magnification, turn the lens around.
You could also try a “macrophoto” lens for still cameras. These are lenses that work with magnification ratios of 5 or 10 or more, but they are designed to be closer to the object than to the camera. You use them with a bellows. A good camera company like Canon or Nikon should have them on their web site. I have used them and they are very nice and fun, and they are dozens or possibly a few hundreds of dollars. The front of the lens is usually small and tapered, like a microscope objective, but usually 2 or 3 times bigger, and usually black. The front lens element is 1/4" or so in diameter. Look for focal lengths like 20 or 30 mm.
You could also try putting two still camera lenses together, front-to-front. They sell filter rings with male threads on both ends that let you do this, and also some adapters to put on what was the camera end of each lens to take care of the auto stop down lever and other details, which may help.
Finally, I think you want a thin lens to be TWICE the focal length away from the object and away from the image, but am not confident about it.
Forgot to say that Edmund Industrial Optics also sells parts like lens elements and assemblies and threaded tubes and iris diaphragms and even cameras. They also do custom design.
Much of their stuff still feels a little cheap, and last I heard some of the Edmund family is still involved, especially a ditzy sister in there somewhere I think. Bob is not much involved, dad is long gone, and they never call themselves Edmund Salvage any more. They are also tied to some other company called Anchor Optics that kind of looks like a bored sibling wanted their own operation, and the distinction in the missions of Edmund Industrial Optics and Anchor Optics seems pretty thin and ignored. But they do seem intent on at least looking like a real, professional operation, like Newport (and the old Oriel) and Thorlabs. If you take them with a grain of salt, they may be a useful vendor or even subcontractor.
My knowledge is mostly in the field of macro photography so I wouldn’t know if there are specialized constructions that are more suitable for you. My advice if you want to use photography lenses, which should work perfectly fine if you can find suitable adapters, or craft your own mounts, is similar to Napier’s. Since you don’t need a magnification higher than 1:1 any macro lens should do (for example Nikon, Canon, Tokina, Tamron, Sigma), with the desired focal length depending mostly on your preferred working distance. In general almost all macro lenses have excellent sharpness. For shorter focal lengths they might not cost more than $250-300, while the cost increases steadily if you need longer working distances.
If your budget is tight, there might be even cheaper solutions that are still satisfactory. For example, if your working distance requirements are not too long, it might very well be good enough to mount a 100-150$ 50mm lens in reverse (by using a reverse adapter, or something homemade) and use a short extension to reach 1:1 magnification. I don’t have the extension requirement in my head, and it depends slightly on the exact lens used, but should be somewhere between 10 and 20 mm. I use this technique myself for macro photography of small insects and other things, and the results are in my opinion plenty good. Although, I have no idea what resolution requirements you have.
If you use a lens meant for regular camera use, it will probably be helpful to get a lens with an aperture ring so that you don’t need special electronics to change the aperture size.
That is one option - especially if cost is a big factor. I’ve done it myself with a Nikon-F to C-mount adapter. But SLR camera lenses aren’t really optimized for small high-resolution digital cameras. The camera referred to in the OP is smaller than 35mm film, and higher resolution. So it may not be quite sharp enough for the application. (Actually the pixel size is similar to a consumer DSLR, but it’s a monochrome camera, so the effective resolution is better.)
Although most C-mount lenses aren’t sharp enough either. Traditionally the C mount was used on video cameras (CCTV and similar applications), so most C-mount lenses are only good for TV resolution. However, there is a decent selection of “megapixel” C-mount lenses which I think would do the job.
You could take the easy option and buy one (or several) of these for around $1500 a pop. It’s not really intended for taking videos, but it has both a USB out and an analog video out, so it will work. The microscope is pretty basic, but it does what you need it to do.
No decisions yet… still trying to figure everything out, and it’s not a very high priority at the moment.
Actually, the Leica EZ4 might be exactly what we need, just as long as we can get the images off the way we need. (To be a little more specific, we’re not really taking videos in the normal sense, but we want a frame every 10 seconds for many hours). I may hit up the Leica rep around here and see if he can let us try one out…
The software you need is Leica’s Multi Time. I’ve never used it and I have no idea what the price is (probably not free ). If you’re in Texas, the Leica guy in Houston is a great place for a science geek to spend a few hours.
For the two or three of you which still might care, we ended up deciding on one of these from Meiji. Pretty much exactly what we needed. The optics were a bit more expensive than we could get from the more generalized suppliers, but it comes with exactly the sort of stand and lighting we need (which I was going to kludge together otherwise…)
I very much recommend this solution, which will provide the encessary magnification with a high quality and a low price. Find a lens whose focal is about the diagonal of your sensor (should be amongst the cheapest) and put it on the cam, then chose a lens with a slightly lower focal length if possible (e.g. 2/3 of the first lens) of the focal. Revert it and adapt it one way or another. I don’t think that you will need to control the aperture of the inverted lens, by the way.
The inverted lens will basically act as a (high quality) magnifying glass.
The ‘equipment’ section ofthis wikipedia pagelists this solution, amongst others.
Otherwise, a custom-made macro bellow may also be a good solution. Since you can easily find simple lenses for your camera which have a manual diaphragm control and you will have a fixed setup, you don’t have to worry about the camera and the lens having to communicate.
About $2.5k all told. With more general-purpose optics, we were looking at more like $3.5k if we used off-the-shelf stands that wouldn’t be very good for our purposes, and $1.5k with lots and lots of kludging together. Which I could do, but hey, it’s not what I’m paid for, and we have a grant specifically to pay for this setup.
We’re going to use these to watch nematodes (little tiny worms) crawl around the 4x6 mm chamber, for 12 hours at a time. That way we can experiment with long-term behaviors which would be impossible to observe with the usual grad-student-staring-into-microscope apparatus. And the other groups in our lab won’t be mad at us for monopolizing the one microscope that can do this currently.
). If you’re in Texas, the Leica guy in