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posted by cmn32480 on Friday November 06 2015, @03:35PM   Printer-friendly
from the far-far-away dept.

Telescope mirrors of old basically came in one shape: they were round and fit nicely inside a tube. No longer. An emerging optics technology now allows these light-gathering devices to take almost any shape, potentially providing improved image quality over a larger field of view -- all in a smaller package.

Called freeform optics, this emerging mirror technology, brought about by advances in computer-controlled fabrication and testing, has triggered a sea change in optical engineering. Seeing the benefit of "potato chip-shape" or asymmetrical optics, NASA optical engineers at the Goddard Space Flight Center in Greenbelt, Maryland, have moved quickly to establish an expertise in this emerging technology.

"The use of freeform optics can significantly reduce the package size as well as improve the image quality," said Joseph Howard, who is working with Goddard engineer Garrett West to ultimately design, integrate, and test a two-mirror freeform optical telescope for imaging and spectroscopic applications.

http://www.eurekalert.org/pub_releases/2015-11/nsfc-owt110515.php

[Also Covered By]: PHYS.ORG

[Source]: NASA Goddard


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  • (Score: 2) by Nuke on Friday November 06 2015, @06:38PM

    by Nuke (3162) on Friday November 06 2015, @06:38PM (#259580)

    The circular shape is not essential, but it needs to be parabolic. Whatever, the amount of light collected will be proportional to the mirror area and there is no substitute for that. Make the same area square if you like. Would someone offer to explain why an astromical telescope would have an advantage in not being axi-symetric? I'm all ears, seriously.

    The links are short on detail, and the NASA one did not work for me. However I was NOT impressed when they went off at a tangent to explain what 3D printing was, like it's a new idea.

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  • (Score: 4, Informative) by Anonymous Coward on Friday November 06 2015, @07:42PM

    by Anonymous Coward on Friday November 06 2015, @07:42PM (#259608)

    Parabolic shape is not important either, as long as you have another optic down the line that corrects the aberrations put in by the upstream optics. I think the idea here is that you can have a funky-shaped mirror, then you can follow that with other funky-shaped mirrors to correct and focus the image (or spread out, in the case of a hyperspectral sensor).

    The advantage of a non-axialsymmetric astronomical telescope is that you can get rid of the central obscuration. That obscuration cuts down on the light you receive, and it cuts down your Modulation Transfer Function [spie.org], which basically means it lessens your resolving ability. There are some other advantages [google.com] to do with aberration correction (see, for instance, the table on Slide 31) as well. That PPT package has got a lot of good stuff in it, but just the first few slides as well as the layouts of the different telescope designs makes it interesting enough.

  • (Score: 0) by Anonymous Coward on Friday November 06 2015, @07:43PM

    by Anonymous Coward on Friday November 06 2015, @07:43PM (#259610)

    Axi-symmetric would place the secondary reflector in the field of view, which in turn reduces the quality of the image (e.g. diffraction effects). An asymmetric design could put the secondary off axis more easily - consider a Herschelian reflector as an example (
    http://www.telescope-optics.net/tilted2.htm/ [telescope-optics.net]