US PATENT SUBCLASS 359 / 749
.~ Reverse telephoto

Current as of: June, 1999
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359 /   HD   OPTICS: SYSTEMS (INCLUDING COMMUNICATION) AND ELEMENTS

642  DF  LENS {32}
749.~ Reverse telephoto {4}
750  DF  .~.~> With eight components
751  DF  .~.~> With seven components
752  DF  .~.~> With six components
753  DF  .~.~> With five or less components

DEFINITION

Classification: 359/749

Reverse telephoto:

(under subclass 642) Subject matter wherein the lens is designed with the effective focal length equal to or less than the distance from the last refracting surface to the focal plane, i.e., the back focal length is equal to or greater than the effective focal length.

(1) Note. This is also known as a retrofocus lens and it consists of an ordinary objective with a negative component near its focal point, thus forming a large back focus

relative to its focal length.

(2) Note. The focal length is the distance from the principle focus (focus of parallel rays of light) to the surface of a mirror or the optical center of a lens.

(3) Note. A focal point is the point at which a lens or mirror will focus parallel incident radiation.

SEE OR SEARCH THIS CLASS, SUBCLASS:

643+, for eyepieces.

648+, for projection type field curvature shaping lens. 656+, for microscope objective.

680+, for reverse telephoto lens of variable focal lengths.

708+, for a nonspherical lens.

733+, for multiple component lenses having a reflecting element.

745+, for telephoto lens.

754+, for multiple component lens systems generally.