Lensman. E.E. "Doc" Smith. Classic space opera with pure-as-Boy-Scout heros and unrelentingly evil bad guys fighting for control of planet-squishing "doomsday devices."
Apochromatic lens: Compound lens corrected for chromatic aberration, i.e. the three primary colours , red, green and blue are corrected. Also called Apochromat.
A physiotherapeutic apparatus for preventing and treating near sighted eye has a convex lens used as objective lens, lens cone, eyepiece, headgear and lens set.
By chiseling a BOL on a surface of a lens, a apochromatic system is composed, which actualizes the system's apochromatism, as well as revising primary aberration.
During this alignment, each crystal can act like a miniature lens, refracting sunlight into our view and creating phenomena like parhelia, the technical term for sundogs.
According to the properties of basic points of lens group and the varifocal principle of lens group,a varifocal optical system which has a fixed image space principal point has been designed.