How to concentrate white light in a very small point?

  • #1
Good morning everyone. I have a question for the community. I am doing an optical project in which I need, as the title says, to concentrate white light in a very small point, with a diameter of the order of microns, so that I can pass light through a pinhole. I've been trying it with some lens sets using a halogen lamp but I can not get a point small enough. How could I get this? I would greatly appreciate if you can, in addition to advising me on this issue, send me some bibliographical sources from which to consult, thank you very much.
 

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  • #2
berkeman
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Welcome to the PF.

Others can give you better replies, but are you familiar with spherical and chromatic aberrations in lens systems? At a minimum, I would think you would need to use a compound lens that had these corrections. Do you have access to a good quality camera lens (detached from the camera body)? What lens diameter are you looking to use? What is your object distance (to your light source)? What is your light source?
 
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  • #3
Ibix
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If memory serves, the smallest spot size you can produce with a perfect optical system is given by the Rayleigh criterion. My back-of-the-envelope calculation suggests that your aim is rather ambitious.
 
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Others can give you better replies, but are you familiar with spherical and chromatic aberrations in lens systems? At a minimum, I would think you would need to use a compound lens that had these corrections. Do you have access to a good quality camera lens (detached from the camera body)? What lens diameter are you looking to use? What is your object distance (to your light source)? What is your light source?
I am using a halogen lamp, but I also have available LED sources and even a Xenon lamp. I´m using the optics laboratory so i think i can get that special lens.

I'm doing the montage of a Czerny-Turner monochromator and for that I need to collimate the white light with a spherical mirror (I attach an image of this)
300px-Czerny-turner.png

Here I have another question, what effects will it have on the collimation of light and on the operation of the grating (D in the image) if the point of concentrated light (see point B of the image) is not very small?

Thank you so much
 

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  • #5
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white light in a very small point, with a diameter of the order of microns, so that I can pass light through a pinhole
A point source of light will produce parallel rays upon reflection from a parabolic mirror.
You don't have appoint source ie the pinhole becomes the source of light, and the spherical mirror is an approximation of a parabolic mirror as long as the curvature is not too great.
As it is, any light that passes through the pinhole will be somewhat collimated upon reflection from the spherical mirror.
Question is - how strong of a light source ( ie pinhole ) do you need, and does all the light from the halogen lamp have to go through the pinhole.
 

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