Thanks for the clarification.

But in this case 'd' is small when compared to R1 and R2, so can I use this
formula

1/f = (n-1) {1/R1 - 1/R2} ???

And again I have calculated the focal length using the actual formula which you
have mentioned... Now how can i place the lens in the exact length (focal length
say f=216) to get sharp and better image.



Le_Forgeron <jgr### [at] freefr> wrote:
> Le 21/10/2011 07:46, Arun Kumar nous fit lire :
> > Thanks again for your help.. It helped me a lot. I have created lens and front &
> > side views which am exactly looking for. Now i need to calculate the focal
> > length of the lens. How can i calculate the focal length.
> >
> > To calculate focal length manually there is a formula
> > 1/f = (n-1) {1/R1 - 1/R2}.
> >
> > But how can i calculate it from the code.
>
> The formula is wrong. (or rather, you forgot the interesting part)
>
> it's
>
> 1/f = (n-1)( 1/R1 - 1/R2 + (n-1)d/(nR1R2))
>
> (if I was to trust wikipedia :
> http://en.wikipedia.org/wiki/Focal_length
> )
>
> R1 & R2 are the radius of the sphere.
> d is the thickness of the intersection (at the line connecting the spheres)
> n is the ior
>
> Numeric application from previous code:
> R1=6;
> R2=6;
> d=1;
> n=1.5;
> notice that 1/R1-1/R2 is null;
>
> 1/f = 0.5 ( 0.5*1/(1.5*6*6)) =
> .00462962962962962962962962962962962962962962962962962962
>
> or f= 216
>
> Units (meter, foot, pov-unit) are irrelevant as they all ends up in the
> same space (a linear length).

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