A lens made of crown glass and usually forming one component of an achromatic lens.
- After polishing the crown lens, a new lap - convex - is made and the third surface polished.
- After crown lenses are chemtempered, suspend them over the chemical bath for at least 15 minutes.
- Now lower the mating surface of the crown lens onto this puddle without entrapping air and let the lens settle into the oil unaided.
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