Lens Center Thickness

[navullav]

Hi guys, anyone has the formulation on how center thickness of a lens is derived from edge thickness ?

[HarryChiling]

Hi guys, anyone has the formulation on how center thickness of a lens is derived from edge thickness ?

What you would be looking for is the saggital depth equation

Sag=saggital depth
r=radius
d=diameter of the lens
p=aspheric coefficient
n=index of material
x=decentration

Spherical Sag
Sag=r-sqrt[r^2-(d/2)^2]

Approximation
Sag=[D*(d/2)^2]/[2000(n-1)]

Aspheric Sag
Sag=[r*(x)^2]/1+sqrt[1-(p*(x)^2*(r)^2)]


Once you have found the sag of a lens you can then determine the center or edge thickness

ct=center thickness
et=edge thickness
sag=saggital depth of lens

Plus Powered lens
ct=et+sag

Minus Powered Lens
et=ct+sag


Hope this helps if you need more info check out www.technicalopticians.org and do a search for "saggital" , or download all the equations.

[Snitgirl]

Can you type out the Canadian version of this formula? lol :D

Thanks

[HarryChiling]

Snitgirl, I have a question for you.

Did you attend Vision Canada 2006? If you did what did you think about it?

[navullav]

Thanks Harry.I will try the attached formula.

[Snitgirl]

Snitgirl, I have a question for you.

Did you attend Vision Canada 2006? If you did what did you think about it?

Hi Harry. :) I was going to but wasn't able to make it. A few of my friends went and stated that the attendence was slim to none. Also mentioned they had about 15 exhibitors and around 15 lectures.

Not sure if its going to be the same (small) for Vision Canada Niagara Falls - September 9th-10th, 2006, hope not especially since Canada is a great destination. Well I think its a great place, especially since I just moved here. :D lovin it!

Michelle