Comment by contingencies
5 years ago
For a markedly less engineering oriented introduction see https://en.wikibooks.org/wiki/Modern_Photography/The_camera
One interesting thing I learned recently is how they make cheap plastic lenses, and the fact that plastic lenses were invented by an Australian. They are created by choosing a polymer with good optical properties and then thermoforming it by carefully applying air pressure to raise a rounded shape to a dome after clamping the edges, then holding the air pressure constant until it has cooled. Because nothing actually touches the lens portion, optical properties are preserved.
Do you mean, like creating a bubble of plastic fed from below where surface tension holds it in a shape like a bubble? And then letting it harden while in that shape? Does the air pressure you talk about mean blowing a stream down onto the lens?
And then, no further polishing is necessary? I'm fascinated to learn more if you have a source to read more from!
You can go up or down (probably sideways if you can account for gravity, eg. through rotary motion). Up is more common since you only need significant equipment on one side and access requirements mean that keeping the bulk of it 'down' is easier. No polishing is necessary. However, I recall reading that some polymers can be polished if you want, but IIRC it depends heavily on the polymer, the abrasive, intermediate fluids in use and result desired. Re: Source, I raided libgen for thermoforming over the last few months, visited about 10 equipment factories and studied their mechanisms and control systems, but actually learned this tidbit from 1000 Australian Inventions or some such book which I bought for my daughter before our family returned to China... to keep inventing ;)
This works for some lens shapes. For most though, molding is necessary.