Hello to all,
I need some help in understanding base curve, true base curve, cx radius and refractive index.
Firstly, in theory which is the wavelength at which a +1D lens has to have 1 m focal length (the green mercury line, e 546.07 nm, or the yellow sodium, d 587.56 nm)?
Then, as for the base curve, I thought that:
- base curve is the base curve referred to a 'reference' refraction index of 1.53 or, sometimes, 1.523
- true base curve is the base curve calculated for the actual refractive index of the material the lens is made
- cx is the actual radius of curvature in mm
If you look at:
http://www.zeiss.com/412568200025873...revity_167.pdf
It seems that I have missed something..
They have listed base curve, that I think are referred to the actual refractive index at d light of the material (?), then true base curve refered to n=1.53 and then cx in mm.
Can anyone explain me which is the correct definition for true base curve?
And in which way I can know the real curvature radius in mm of a semi-finished lens claimed, for instance, to be base 8?
Thank you very much in advance!!
:)
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