Couple questions:
First: Are there digital bifocals? if yes how is the segment applied using free form tech?
Second: Can you apply slab off using free form tech?
Couple questions:
First: Are there digital bifocals? if yes how is the segment applied using free form tech?
Second: Can you apply slab off using free form tech?
Last edited by Keinsohn03; 12-30-2022 at 04:07 PM. Reason: typo
Yes. If you are talking about lined bifocals, the fronts are molded(just like standard bifocals) and the backs are freeform.
There are freeform round segs(I don't know why) all done on the back with a fuzzy blend zone around the seg.
Yes, I hate them. It's not a sharp slab line. It's a couple mm wide fuzzy line. I personally think they are terrible, but they are fast and cheap compared to the traditional.
I am talking about a lined bifocal thank you! So how would this process work if it's using both free form and conventional methods to make it? Do you surface the back first with CNC and then surface the front? (I have no current lab experience but am doing a project and having trouble finding a simple step by step guide to all this)
Is the slab applied during the surfacing phase?
Currently there is no way to create a lined bifocal using a free form generator. A salad off is not something that is applied to the lens. Traditional slab off is created by cementing a slab of material to a lens. Grind a prism on the slab until half of the slab is ground off and then the other half is removed hence the name slab off. Tou now have lens with two centers on the same surface. You can also purchase a plastic lens with the slab cast on the lens the mold used is created the same way as described.
So I've seen online that there are companies that can do free form bifocals but I don't understand what that means then if you can't generate a line.
I also know free form slab off is a thing but then how is that done?
you explained how both couldn't be but then didn't explain the process.
Free form bifocals that are advertised are rd segment on the concave surface. The periphery of the segment is not sharp as is the norm with bifocals except for blended bifocals. You cannot make sharp line with the freeform process that is why you can create a progressive as no sharp lines are wanted. A bicentric grind giving two optical centers on the same lens can be done but once again you will not have a sharp line like a traditional slab off.
Round free-form segments are an option for presbyopic sunglass wearers who don't like PALs...the back-side nature of them allow for mirrors on the front, too...
Kudos 03 for working ahead of the curve! Keep that attitude through life, it will take you far!
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