1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Ideal optical collimation system

  1. Oct 20, 2011 #1
    Hi,

    I have been stuck on a project that I am working on. I am trying to collect light using optics from a FOV of 200x200mm at 200mm distance. I have two major problems:

    1. My detector is small so I need to collimate the light (my application is not imaging so I don't worry about the image), I need to reflect that FOV to a detector that is 2.5x2.5mm in size.

    2. I need to block Sun out. I am using an optical filter but these filters are bad when it comes to angle of incidence.


    Let me describe my current system. I have a cheap fresnel lens that has a 5mm FL and 10mm diameter. I use this to collect more light and send to detector and I put a filter in front of this Fresnel lens. The problem is the filter is not enough, It blocks sun ok however there is still quite a bit of sun comes in and introduces Shot noise. I like to make the light collimated so that I can pass through a very narrow band pass filter and kill the sun's impact almost all the frequencies except what I am interested.

    I have considered ideas such as tapered rod, but this has the same problem as my current system. I need optics to make light collimated and parallel. Any ideas or pointers?

    thx,
    F.
     
  2. jcsd
  3. Oct 20, 2011 #2
    Perhaps there is a language barrier but I really don't know what you are trying to say. You are trying to image something 200x200 mm to a detector of some kind that is 2.5x2.5 mm? Or is collimated light coming through an aperture that is 200x200 mm at a 200 mm distance, and you want to reduce the beam as in a telescope? You need to reflect a field of view, than in some way does or does not contain sunlight? The angle of incidence somehow affects whether or not a filter works? Perhaps if you included a sketch it would be clearer what you are trying to do.

     
  4. Oct 20, 2011 #3
    I used to make telescope optics, and we used a flat mirror in front of our scopes to autocollimate them. What I gather is that you have a lens focusing light on your sensor, but you'd like to collimate it near focus so that it is a compact beam. I think the simplest way to do this is place a lens near the focus. You might get away with using a telescope eyepiece, but if not you should be able to use the basic thin lens equation to find the focal length you need.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Ideal optical collimation system
Loading...