US PATENT SUBCLASS 351 / 169
.~.~.~ Gradually varying focal power

Current as of: June, 1999
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351 /   HD   OPTICS: EYE EXAMINING, VISION TESTING AND CORRECTING

41  DF  SPECTACLES AND EYEGLASSES {29}
159  DF  .~ Ophtahalmic lenses or blanks {10}
168  DF  .~.~ Multifocal {4}
169.~.~.~ Gradually varying focal power

DEFINITION

Classification: 351/169

(under subclass 168) Subject matter wherein the multifocal lens has areas gradually changing in dioptric power.

(1) Note. The lens may have countersink and a segment with different indices of refraction fused therein, or may be formed from one piece or material by providing a continuously varying radius of curvature.