Physics Help Forum Optics for Research

 Feb 20th 2019, 12:48 AM #1 Junior Member   Join Date: Feb 2019 Posts: 2 Optics for Research I have a light beam with diameter of 1mm and I'm trying to reduce it's diameter to less than 50 micrometers (as shown in the image) I was thinking of using one of the high quality camera zoom lens. Any suggestions, or ideas? Attached Thumbnails   Last edited by kordzaia; Feb 20th 2019 at 12:50 AM.
 Feb 20th 2019, 08:26 AM #2 Senior Member     Join Date: Jun 2016 Location: England Posts: 844 Can we assume you want a focus at a screen in which case the "beam" after the lens can be cone shaped and you select the size of the final spot by moving the screen, The strength of the lens is not critical in this scenario. Scenario 2 you have a fixed distance between the lens and the screen here the strength of the lens is critical, a zoom lens might help Scenario 3 You want a parallel 50 micrometer beam after the lens here you will require a precise arrangement of (at least) 2 lenses, one converging, to bring the beam down to size, the other diverging, to bring the beam back parallel, topsquark likes this. __________________ ~\o/~
 Feb 21st 2019, 01:32 AM #3 Junior Member   Join Date: Feb 2019 Posts: 2 It's scenario 1. it can be cone shaped and I can move the screen. Would you recommend any specific lens?
 Feb 21st 2019, 03:52 AM #4 Senior Member     Join Date: Jun 2016 Location: England Posts: 844 The short answer is no. The key point will be the focal length of the lens The focal length tells how far from the lens a parallel beam will be focused to a point. From this and some simple geometry you can work out where the screen must be. You probably have a fair amount of lea-way so any mid-range focal length lens will probably do (not too week, but it does not need to be hugely strong. The only other factor is probably the size (diameter) of the lens. It needs to be bigger than your incoming beam, plus a bit. I would aim for at least double the diameter of the incoming beam, but for your application (incoming beam =1mm) this is unlikely to be an issue. One further thought, is this a laser beam? You have to be very careful focusing even quite low power lasers. at the focus the energy levels can get dangerously intense. __________________ ~\o/~

 Tags cameras, lens, optics, research

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