- #1
Stargazer19385
- 49
- 0
Suppose I want to make a good acrylic lens, with very few bubbles. Could my eyes tell the difference between perfection and standard optical quality acrylic? Would getting it very hot and low viscosity, and then centrifuging it, be a good way to separate out the bubbles and inclusions? How do glass makers improve their quality? I would think getting it hot and full of convection currents would be a good way to get it more homogenous, which is also important.
If I grind it in water to prevent dust and overheating, will the acrylic absorb the water fast enough to have optical problems when the lens is done?
What if I make a glass lens, then a mold, then try to inject the low bubble acrylic into the mold. Does injection usually reintroduce new bubbles? Maybe a hot syringe and vacuumed mold would be in order.
If I have a perfect acrylic lens, which can absorb water from the air, would a 1/4 wavelength AR coating of MgF seal it so that no water can get it?
Would the large thermal coefficient of thermal expansion (about 70x larger) vs the low coefficient of glass mean that the AR coating would flake off if ever exposed to hot car temperatures or freezing overnight temperatures?
And how smooth do you have to get an acrylic lens before fire polishing it can take it the rest of the way? I would probably have a concave similar but negative shaped iron which I heat read hot (or maybe lower, whatever is best) and lower to within 1/4 inch of the lens. I'd watch through the glass window and lift the iron off as soon as the lens looked shiny from surface tension. Then it would air cool. Do you think that would cause enough thermal expansion difference between the surface and core to crack the lens?
I also looked at some custom lens sites, and they reported their scratch/dig ratios and surface tolerances, and I was surprised that even though they offered fire polishing as a surface, they still report having scratches and digs. I would think the surface tension would fix all that.
If I grind it in water to prevent dust and overheating, will the acrylic absorb the water fast enough to have optical problems when the lens is done?
What if I make a glass lens, then a mold, then try to inject the low bubble acrylic into the mold. Does injection usually reintroduce new bubbles? Maybe a hot syringe and vacuumed mold would be in order.
If I have a perfect acrylic lens, which can absorb water from the air, would a 1/4 wavelength AR coating of MgF seal it so that no water can get it?
Would the large thermal coefficient of thermal expansion (about 70x larger) vs the low coefficient of glass mean that the AR coating would flake off if ever exposed to hot car temperatures or freezing overnight temperatures?
And how smooth do you have to get an acrylic lens before fire polishing it can take it the rest of the way? I would probably have a concave similar but negative shaped iron which I heat read hot (or maybe lower, whatever is best) and lower to within 1/4 inch of the lens. I'd watch through the glass window and lift the iron off as soon as the lens looked shiny from surface tension. Then it would air cool. Do you think that would cause enough thermal expansion difference between the surface and core to crack the lens?
I also looked at some custom lens sites, and they reported their scratch/dig ratios and surface tolerances, and I was surprised that even though they offered fire polishing as a surface, they still report having scratches and digs. I would think the surface tension would fix all that.