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Optical Lense (and mount ?)

Discussion in 'General Electronics' started by Quack, Jun 28, 2004.

  1. Quack

    Quack Guest

    Hi,

    I am looking for some kind of lense to mount infront of a small
    photodiode sensor (TAOS surface mount chip) on a PCB.
    I want this lense to allow the sensor to view colors better at a
    distance of 10cm (As apposed to close up, under 2cm), so something
    like a fixed 'zoom' lense i guess.

    So my question is, where would i get such a lense ?, what would it be
    called ? (i have seen the word 'collminating' all over google when
    searching for lenses, is that what i want?), and how would i mount it.
    Are there standard lense mount mechanisms available ? something that
    would sit straight onto a PCB ? what are they called, where can i get
    them :).

    I can blindly stab around at what i want, but if anyone has experience
    with this kind of stuff, please point me in the right direction :).

    much appreciated,

    Alex.
     
  2. Bob May

    Bob May Guest

    Often lenses are mounted on a piece of plastic that mounts to the PCB with
    either screws or clips. There are usually 2 locating pins on the plastic
    piece to insure that the lens is in the right position.
    You want a doublet lens for the lens if you are dealing with colors but a
    single lens will do if you don't need to have an accurate focus on the
    photodiode over the color spectrum.
    Your application is for a finite conjugate setup and the general formula for
    the two focal points and the needed focal length is :
    1/Ffl = 1/Ffp1 + 1/Ffp2
    where:
    Ffl is the focal length of the lens
    Ffp1 is the focal plane of the photodiode (the distance from the diode to
    the lens).
    Ffp2 is the focal plane of the object to be viewed (the distance from the
    lens to the item to be viewed by the diode).
     
  3. Hi Quack!

    For mounting you could use a cage system.
    Screw 2 or better 4 cage rods to the pcboard and put the two lenses in cage
    plates. You can then easily adjust the postition of both lenses. It might be
    a little bulky but also very stable and easy to adjust.

    You can find cage systems at Thor Labs
    h**p://www.thorlabs.com/SelectGuide2.cfm?Guide=5&Section=1&Ref=8
     
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