And/Or: Can progressive bifocals be measured and duplicated?
In: 2
There’s no such thing as “half of a lens”. The reason that lenses work is because every part of the lens does exactly the same thing. The top “half” focuses light to the same place as the bottom “half”. *If* the whole lens has the same curvature.
By simply blocking one of the focal lenses (half of the bifocal) you can study the other half as normal.
While I’m not sure how commonly it is done or what the common practice is, progressive bifocals can easily be measured through a variety of methods. The one that first comes to my mind is taking a laser, slowly scanning the entire lens with it, and measuring how much the beam bends at each point of the lens.
A simplification of this method would be to take a flat laser beam and scanning the lens from top to bottom. Having a screen behind the lens, measuring the width of the beam as it scans through tells us the horizontal curvature at any particular height, and the vertical deflection tells us the vertical curvature at that height. This would be pretty easy to computerize.
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