For those not familiar with this series allow me a moment to prattle on about it. I admit up front that I am quite fond of the platform so there is a bias to be aware of, but I think most will agree that not only are these quite nice instuments, you'll be hard-presssed to find anything comparable anywhere near this price.
In 1961, AO decided to focus their efforts on infinity corrected optics and introduced their 34mm parfocal infinity system at a time when the rest of the industry was focused on using finite tube lengths such as the common 160mm TL microscope. It’s hard to discuss some of the features without an understanding of infinite vs finite, but I’m only going to cover some of the very basic concepts. In an infinity system, the light bundle that comes out of the back of the objective is effectively parallel and it uses a telan lens in the base of the head to convert that parallel bundle into a beam that converges to a focus to be picked up by the eyepieces. What this means is that, theoretically the objective and the head can have a variable distance between them and still work as a complete system delivering a useful image at the correct magnification. This might not seem especially useful at first, but it allows adding various analyzers and other instruments into the path without affecting the focus of the final image, a feature that finite systems struggle with, making the same product capable of a variety of advanced techniques easily by adding modules to extend functionality. There were a lot of these made with a variety of add-ons allowing brightfield, epi illumination, darkfield, phase contrast, fluoresence microscopy, and more just by adding or swapping out components.
An additional feature that’s easy to overlook at first glance is that this allows changing the way focus is achieved. With the 34mm infinity system, AO was able to alter the design so that adjusting the focus raises and lowers the nose instead of the stage while the head remains fixed. This might seem trivial, but it allows something few other systems could achieve; effectively removing the possibility of crushing a slide and objective together and destroying one or both as the nose simply comes to rest on top of the slide instead of being driven into it. Another added benefit is the ability to quickly change objectives and cycle through uniform slides while maintaining focus, requiring only minor adjustment of the fine focus to account for the minor deviations. Here’s an excerpt from the manual, describing the process.
“The autofocus stop is pre-set at the factory. It is the stop which limits the height of the stage. This setting is valid for slides anywhere from 0.50 to 2.5 mm, in thickness. Because of the highly precise tolerances held in the manufacture of the objectives, it is possible to search the slide with 10x or 45x objectives, find the required field for study under oil immersion, raise the coarse adjustment, swing to the oil immersion objective, apply oil to slide, and lower the coarse adjustment rapidly to its positive stop. The subject will be in focus within a touch of the fine adjustment with absolutely no danger of touching the slide.”
This leads to a discussion of the focus mechanism which I personally consider beautiful in it’s simple elegance. Here’s a link to the AO 10 manual (there are other versions of the manual at PS Neeley’s):
https://user.xmission.com/~psneeley/Per ... ersion.pdf
Unlike some manuals, the AO 10 manual is a pretty good resource for getting familiar with using the instrument and is worth a read. It is not a repair manual nor is it an introduction to microscopy, but it does contain exploded parts diagrams which can be quite useful, such as this one regarding the focus which I was just discussing:
- AO10_focus1.jpg (94.26 KiB) Viewed 1668 times
If you study the above image, you’ll see that it is effectively a very large screwform. Within the thread form of the coarse focus rides a ball that is connected to an arm which translates lateral motion of the ball into vertical motion of the arm upon which the nose and objectives are mounted, thus raising or lowering the head as the ball moves from one side to the other. A look at the parts diagram in the back of the manual shows the larger screwform with a smaller and finer screw inside it; the larger is the coarse focus and the smaller, the fine. Rotation of the fine focus moves the block which is the larger coarse focus laterally. Of note, the arm and ball are loaded by gravity; this permits largely slop-free focus and reduces the risk of damaging slides or objectives by accidentally crushing them together. That later being a feature that should stand out to anyone who’s accidentally crushed an expensive/loved slide under an objective.
This series are well built quality microscopes, usual problems with these are frozen greese in the head and focus mechanism, but this one has been cleaned and relubed so that is not a concern.
This series uses AO's 34mm parfocal infinity objectives, a product line AO used for many years over a variety of models. This particular scope is equipped with a 4x/0.12NA Cat.1017 plan achro, 10x/0.25NA Cat.1019 plan achro, 45x/0.66NA Cat.1116 achromat, and a 100x/1.25NA Cat.1079 achromat. For those not familiar, plan objectes provide a "flat field" over most of the field of view where an achromat that isn't plan will be in focus at the center, but the periphery will become more and more out of focus.
This unit comes with a 1.25NA Abbe condenser Cat.1088 with an optional swing-in auxilliary lens to fully illuminate the field for the 4x objective. Of note, the swing-in aux lens is NOT the original AO one, but rather a new replacement which I created detailed here:
viewtopic.php?p=120232#p120232
The stage is the standard mechanical stage. The focus knobs are marked with 1 micron increments, which provides measurement in the Z axis.
The illuminator is the Cat.1036, 6V 17watt tungsten lamp; it does not have a field iris as the Cat.1036A does, so full Koehler illumination is not possible without replacing the illuminator. The 1036 illuminator does include a built in neutral density filter (10%) to cut the light intensity more, which is nice for low power viewing. Included is a Cat.1051 transformer to provide variable voltage to the lamp.
The head is a binocular, trinocular heads are easy to install and typically not difficult to find, but I don't have any more spares so cannot offer the option.
The scope comes with a pair of 10x Cat.176 eyepieces. A pair of 15x Cat.184 eyepiece can be included for an extra $35.00
This microscope is used and shows signs of wear and has a few nicks and blemishes as one would expect from an instrument that's 50 years old. It's in good serviceable shape and everything works as it's supposed to. I believe in the value of these scopes enough to offer that if you aren't happy with it, you have 60 days to send it back and I'll refund your money.
I always throw in a few extras, a box of KimWipes, a litle 3D printed holder for 32mm filters, a 3D printed eyepiece case, and a poorly made slide of some Chrysops fly parts (the same slide used for the images).
Now for the images....
- AO10_1.jpg (178.7 KiB) Viewed 1668 times
- AO10_2.jpg (112.67 KiB) Viewed 1668 times
- AO10_3.jpg (105.64 KiB) Viewed 1668 times
- AO10_4.jpg (138.18 KiB) Viewed 1668 times