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Hi index lenses have a higher
“index of refraction.” The index of refraction dictates
how light is bent and passes through the lens. With
plastic high index lenses the denser the material the
slower light is bent and passes through, therefore the
lens has to be thinner to provide the same visual acuity
of a thicker lens that bends light faster. However, the
denser the material the harder the coatings have to be
to prevent scratches. Some coatings are so hard that
they do not take tints well. Higher index refractions
also create more reflections: in some cases AR is
mandatory. The Most commonly used High Index lenses are
1.60, 1.67, 1.71, 1.74. Indexes with a 1.53 to 1.57 are
considered mid-indexes |
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Hi index lenses have a
higher “index of refraction.” The index of refraction
dictates how light is bent and passes through the lens.
With plastic high index lenses the denser the material
the slower light is bent and passes through, therefore
the lens has to be thinner to provide the same visual
acuity of a thicker lens that bends light faster.
However, the denser the material the harder the coatings
have to be to prevent scratches. Some coatings are so
hard that they do not take tints well. Higher index
refractions also create more reflections: in some cases
AR is mandatory. |
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