Gerber Innovations - Computing Front Curve

[Brent Dabney]

Ok so here's the deal. I am trying to do a bi-concave lense but my lab uses Gerber's Innovations program to run throughout the generator. I could let specials lab do it but it's been two times and they have made it on to flat of a front curve.

Rx:
OD: -18.75 -1.00 x 065
OS: -20.25 SPH
PD: 65

Frame: Round Plastic
A: 49
DBL: 17
B: 49

I cannot figure out how to make Innovations able to grind the front curve as well as the back curve, If anyone has any responses it would be appreciated!!

[shanbaum]

You'll have to do this in two surfacing steps, both of which are treated as back curves.

Start with a plano base blank, and grind a lens of whatever power you want the eventual front to be - e.g., -4.00. Set the minimum center (or specific) thickness to something high (in Thickness Options on the Rx page) - say, 10mm.

Once you've completed that surface, you can measure the lens in a lensmeter (if you've used a plano front, you don't have to worry about the power of the front). That's your new front curve. You're probably set to use 1.53 front curves, so you need to convert your measured surface power to a 1.53 curve (that's easy, just multiply the curve by 530/x where x is the material index - 1, times 1000; for example, if you're using CR39, it's 530/498).

Then, when you enter the actual Rx, you can specify the front curve on the blanks page, at the end of Rx entry - after you've specified a blank, or Innovations has selected one, just select "Change Lens Characteristics" from the menu, and change the curves and thicknesses (remember that you need to be logged in to access those bits) to match those of your custom-made semi-finished blank.

[Brent Dabney]

I wound up ordering a set of X-cel High Index -2.25 front curve. The lens blanks we had in stock at the time weren't thick enough to do both surfacing, Thanks for your input though!