Microscope design questions

[Plasmid]

This question has been in the back of my mind for a while.
Aside from the benefits of limiting movement, vibrations of the stage and sample, are there any other benefits to having a microscope where the stage is fixed and the objectives move up and down? Also is there a name or term to describe or call one (moving stage?) vs the other ( moving objectives) ??

[apochronaut]

The stage is maintained at the same height at all times and the stage has more latitude of potential movement if changes in the stage height need to be made. One easy example is the lowering of the stage on a dovetail to accomodate an objective set of longer parfocality. Such is only possible with infinity corrected systems, since the movement of the objective is irrelevant to the tube length.

[Plasmid]

Thank you Phil, you wouldn't happen to know if there is a name for that specific design like in the case of the Reicherts?

[microb]

This question has been in the back of my mind for a while.
Aside from the benefits of limiting movement, vibrations of the stage and sample, are there any other benefits to having a microscope where the stage is fixed and the objectives move up and down? Also is there a name or term to describe or call one (moving stage?) vs the other ( moving objectives) ??

Thorlabs calls it a motorized focus: https://www.thorlabs.com/newgrouppage9. ... up_id=8566

Otherwise it's on inverted microscopes as it is easier to keep the stage level static.

[Plasmid]

Thank y'all

[75RR]

.
A search came up with the terms tube or barrel focus. Can't say I have heard these terms bandied about though.

[apochronaut]

The stage is maintained at the same height at all times and the stage has more latitude of potential movement if changes in the stage height need to be made. One easy example is the lowering of the stage on a dovetail to accomodate an objective set of longer parfocality. Such is only possible with infinity corrected systems, since the movement of the objective is irrelevant to the tube length.

Just elaborate on the history a bit.

In the modern era, AO started using the objective focusing system with the introduction of their series 10 around 1962. Reichert did not use it. The concept became associated with Reichert when the AO factory name was changed to Reichert around 1985. The microscopes didn't change, just the name. Cambridge Instruments , which had purchased the scientific holdings of Warner Lambert, realized that Americans were lustfull for imported goods, believed in the Japanese miracle and were developing an inferiority complex regarding their own design and engineering. Terrible bloated gas guzzling cars were the cause of that perception. If American Motors couldn't make a car that ran for more than 10 years , how could American Optical do any better, huh? Japanese and German stuff were perceived to be better, so swapping the name to Reichert was a cynical marketing ploy on the part of Cambridge. It was all o.k. because AO owned the Reichert factory in Austria. In fact for a while, AO 34mm parfocal infinity corrected objectives were manufactured for both the AO, objective focusing system and the Reichert Austria, stage focusing system. They were in a barrel that could receive either a spring, so could be spring loaded for the Reichert microscopes or a spacer and have a fixed nose for the AO microscopes, where the entire nosepiece floats. They were AO designed objectives, made in Austria and can be found on both sides of the pond in the respective format of the prevailing market and look identical, except for the spring.
Previously, most horseshoe microscopes had used objective focusing because the objective and eyepiece are connected in a fixed tube, so the entire tube was focused but usually with a focuser that was well up on the arm. This was fatigueing for researchers and those that spent long hours at the microscope. In the early 30's Spencer Lens Co. was purchased by American Optical and received an injection of capital. One of the first projects that money was spent on was to modernize the research microscope. Up until then at Spencer, the flagship microscope had been the series 7 with standard high focus. In the early 30's they retained the binocular series 7 for the old guard who were used to it and liked it but remade the old monocular series 5 research stand of the Spanish Influenza era , into a binocular research stand with a low fine focus. The arms could be rested on the bench and still work the fine focus for those long hours of detail hunting that microscopic research entails. It was built into the 33 monocular, the 3 small research stand, the 5 large research stand and the uber rare 8. This entailed a super precise and rather complicated lever mechanism installed up through the arm of the microscope in order to control the optical tube for fine focus.

When AO designed the series 10 ( and subsequently, the 20), they went back to the concept of the low focus activating the optical tube, which was possible because of the infinity optical system. Every microscope made by AO since then has maintained that standard. Even the ATC 2000 student microscope, which was only ever branded Leica, used the same cincept. Obviously, they believed in the importance of a rigid, fixed stage of consistent height.

The only outlyer was the series 2/4, which has a focusing stage built between 1955 and 1962. Since the series 2/4 has finite optics, yet was designed as a mainstream reversed microscope with low focus controls, it pretty much had to be what has become a conventional fixed tube concept, with a focusing stage.

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