From: himansu@gmail.com   
      
   On Saturday, July 7, 2007 at 11:23:46 PM UTC-5, wadex...@provide.net wrote:   
   > On Jul 7, 11:29 pm, Farsang  wrote:   
   > > Hi Michael:   
   > >   
   > > This is primarily for image analysis, but would like also to do   
   > > Physical Optics to simulate better the real situation.   
   > >   
   > > This is the application:   
   > >   
   > > We'd like to get spot size of dia = 2 Cm - 5 Cm (absolute Max) at a   
   > > minimum distance of 100 feet (ideally 250 feet) from the fiber.   
   > > Fiber output power is 200 W and wavelength = 980 nm.   
   > >   
   > > I was thinking to get the required spot size using Geometric Image   
   > > Analysis of ZEMAX and then do the physical optics   
   > > for closer simulation.   
   > >   
   > > Because of the optical invariance it'll be difficult to achieve the   
   > > above spot size using catalog optics.   
   > >   
   > > Do you have any idea how we could get this spot size, appreciate your   
   > > suggestions and comments?   
   > >   
   > > Ideally we'd like to have   
   > >   
   > > Spot Size = 2 Cm - 3 Cm at 250 feet   
   > > Power in the Spot = 200 W   
   > Hi Farsang,   
   > If you are doing imaging analysis, you can model the output of a   
   > fiber as follows: Go to the Field Data box and click on "Object   
   > Height". Enter enough field points to represent your fiber, perhaps   
   > by a point in the center of the fiber, at the .7 zone, and at the   
   > fiber's edges. Set your wavelength in the wavelength box. In the   
   > Lens Data Editor, set the distance from your fiber face to the next   
   > lens or point of interest. Set the fiber's numerical aperture by   
   > setting   ,   
   > . Make the fiber's output telecentric by   
   > clicking on "Telecentric Object Space".   
   > If you are looking for the footprint of the light through all of   
   > the lens surfaces (and the image plane, if there is one), you'll have   
   > to go to   , set the   
   > Field Size: to 0.500 (if your units are set to millimeters), set the   
   > File: to CIRCLE.IMA, set the Image Size: to the size of your area of   
   > interest at a particular surface, then set Surface: to your surface of   
   > interest.   
   > If you are coupling the fiber's light into another fiber, set the   
   > NA in the    box to the   
   > numerical aperture of the fiber being coupled. That will let you see   
   > the coupling efficiency.   
   > If you are doing physical optics propagation, you'll have to wait   
   > for Michael's reply.   
   > But from your last post, I think I see what you are doing.   
   > To model the optical system, if you need a 3 cm spot at 250 feet,   
   > from a 0.5 mm diameter source, your optical system's focal length   
   > needs to be about (250/30)* 0.5 (sorry about the mixed units) = 4.16   
   > feet. At a numerical aperture of 0.22, your system's aperture needs   
   > to be about 23 inches in diameter. It might be hard to come up with a   
   > 23" diameter f/2.27 diffraction-limited lens. It's not impossible,   
   > but it would be expensive. Even the military might want to see a   
   > better solution.   
   > The problem arises from the size of your source. You'll get a lot   
   > further if you use the output of the diode directly (whose source is   
   > effectively the size of a bacterium), without passing it through a   
   > fiber, if that is possible.   
   > Wade Kelman   
      
   Hi Wade,   
   I am working on something similar. I can do the geometric image analysis with   
   CIRCLE.IMA. But what you described will give me the beam profile at the image   
   plane for one field. If I have to get superposition of all the  field points   
   so that I can have    
   the geometric image of the fiber core at the image plane, what do I have to do   
   in Zemax?   
      
   Thanks   
   Himansu   
      
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