Monday, January 18, 2016

Stereo Microscope Shootout!

It's Dick's fault! I've mentioned him several times in the blog - we've been friends for a few decades and share an interest in most things that have lenses or other optics in them. A few weeks ago he forwarded a link to some he thought might be interested in a source for stereo microscopes for only $25! He was amazed that you could get any sort of a working microscope with glass lenses for that price. After it came, he was so impressed he ordered a second (holiday season, you know!). After the second was ordered they sent him an e-mail noting that he was such a good customer, they offered a 10% discount on a third - which he promptly ordered!

Now no one needs 3 stereo microscopes unless you plan on giving them away, but he was also interested in noting not only their optical quality, but there uniformity of quality. He had me over to look thru the first one and I had some issues with combining the images into a single image - what you might expect looking through a $25 optical instrument.

After that first session with him, I was reminded that I had a stereo microscope too! It is an antique, or at least old Bausch and Lomb... I obtained it about 3 decades ago - an estate willed to the Optical Sciences Center where I worked at the time. Many of the items the family didn't want was up for silent auction, and I bid on some books, the microscope and a card table which served me well for nearly 2 decades (and still does!) to hold the slide projector at the Grand Canyon! I don't recall what I paid for all, but it couldn't have been much - a few bucks for the books and card table, perhaps $50 for the microscope. After using it perhaps once in those 30 years, I got it out again after Dick's piquing my interest again.

It is a great little system - a stereo microscope that has a full optical system for each eye (called a Greenough-type). Designed for lower powers, it runs from 7X to 112X with 6 objectives (5 of which can be swapped in/out of the turret), and 2 sets of eyepieces (10X and 15X).  At the lowest power its field-of-view is about the size of a quarter, and you get a true 3-D effect, since each eye sees a slightly different angle. A prism cluster atop the turret housing allows for inter-pupillary adjustment and also erects the image. The patent numbers (the earlier one for the turret design, and the second for objective mounting design) indicate the designs were granted to Bausch and Lomb in the mid-20s and mid-30s, so the microscope could well be up to 80 years old.

While the optics seem to be simple singlets or doublets and all are in need of some cleaning, they perform very well! The eyepieces are simple 2-element Ramsdens, and I can't tell about the objectives. At left is a view of the high-power 7.5X objective that shows how the lenses have flat spots in them so that they can be mounted closely enough to operate at higher power... And at right is a close-up of the turret and the 3 positions of the objectives - a built-in 0.7X and two changeable dovetail-mounted ones.

Well, Dick wanted to do a close comparison of my B&L, his brand new version from Explore One, and likely a 40s or 50s vintage Zeiss version that incorporates a zoom system too. Dick also had a new pair of 15X microscope eyepieces - of modern multi-element design to try as well. Unfortunately, I had some photos of our "stereo microscope Shootout" but accidently erased them after assuming I'd downloaded them (first time that has ever happened!). But we took careful note looking at pocket change through them all. My 80-year-old B&L certainly wasn't left in the dust by newer designs, and when paired with the new 15X eyepieces were just as good. Dick even had an Ebay link to a fellow selling the very same eyepieces if I decided to jump into updating my older system.

3D Anaglyph - get out your red/blue glasses!
I was really impressed by the 3D effect demonstrated by all the microscopes. True, all coins have a non-flat surface, but I was just surprised by the depth. Looking at the Connecticut quarter, the big old Charter Oak was an amazing 3D view of intertwining branches. Being the 3D nut that I am, I tried to take images thru my microscope to make an anaglyph, but failed miserably. Even using a macro lens, I had difficulty, the image shown at left my best effort of the quarter for the Bombay Hook National Wildlife Refuge quarter - the newest-minted. Using the red/blue glasses you can see some depth - a raised rim, with stamped letters, and the bird raised above the background. Almost as good as with the microscopes. I don't know if I'll get into microscopy as much as Dick has, but if I do, I know who to blame!

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