Mirror microscope ?

[georgetsmurf]

I just watched the most amazing documentary about the history of astonomy telescopes. I never knew that it was Newton who produced the first reflective telescope to elliminate the problem of varying refractice indices effect using lenses. I also didn't relise the very basic and now obvious way that a lens (foundation of the reflector) is initially produced by centrifugal forces subjected to molten glass to produce the near perfect parabolar, then the way glass is randomly polished to produce it's near perfect surface which is then coated with evaporated aluminium to achieve the near 100% reflectivity.
Why don't we see this type of technology on microscopes especially when the object we are looking at is stationary much of the time so that we can throw enough light at it to enable the use of optimum apertures. Can anybody throw more light on this (parden the pun).

[Craig Gerard]

George,

You would be referring to the documentary that concluded with some details of the LBT 'Large Binocular Telescope', I presume...

http://lbtwww.arcetri.astro.it/movies/L ... EP2010.mp4 (32.32MB)

http://en.wikipedia.org/wiki/Large_Binocular_Telescope

http://lbtwww.arcetri.astro.it/videos.htm

http://www.youtube.com/watch?v=SvnQtkQEGBU


Craig

[soldevilla]

hello. You're talking about reflecting telescopes. It is true that Newton was the first to manufacture and that was the first successful solution to the problem of chromatic aberration.

This solution is used in microscope objectives. There are lenses with a design based on the Cassegrain design to prevent chromatic aberrations. According as they are carved the surfaces even can be eliminated also the geometric aberrations.
I see two problems with these lenses: The out of focus light points are no longer blurred circles of light, but donuts ... and surely the price is too high for me

http://www.newport.com/Reflective-Micro ... talog.aspx

[ysengrimus]

The obstruction isn't really a problem. It doesn't turn Airy disks into doughnuts, at least not terribly close to focus, it just diverts light from the central disk into the outer rings. The doughnuts don't show up until very far away from the focus. Of course, these things are ridiculously expensive, at least by my standards ;-). Even a 50% (by diameter) obstruction isn't a huge problem, at least for photography.

I find myself wondering if a Newtonian could also be used, and since I have a few lying around...

[rjlittlefield]

Reflecting objectives are routinely used in some applications. You can even buy them at Edmund Optics, for example their TECHSPEC® ReflX™ Objectives, which are derived from the long-lived Beck/Ealing line that was acquired by Edmund in 2010. See HERE for some discussion.

However, when I had an opportunity to work with one such objective a few years ago, I discovered there were some downsides other than cost. As I wrote here in the forum

All these aspects combined to give me very high expectations about how useful such a lens would be for high magnification stacking. I was delighted when I was able to snag a used one on eBay.

My delight disappeared when I received the lens and started testing it. The quality of image was inferior to an inexpensive 10X NA 0.25 achromat, there were significant changes in perspective with focus that caused problems for stacking, and with open illumination, it was very difficult to baffle the lens to prevent stray light from getting past the mirrors. After several iterations of "try this, try that", I gave up and returned the lens for refund -- I believe only the third time in my life I've done that.

I'm sure the lenses are great for their advertised purposes ("Ideal for laser beam delivery"). And it's certainly possible that the unit I received had degraded over the years, say through warping of the mirror block. But for my purposes the experience turned out to be such a waste of time that I won't be exploring that route again.

--Rik

Edit Sep 16, 2019: fix broken links