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US 2010/0165489 A1Published application
Fresnel lens and injection mold
AssigneeCanon Kabushiki Kaisha
InventorsShuusuke Tobita, Yusuke Ohmura
Life of this patent
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Abstract
A surface of a base material of a Fresnel lens has a central area having circular zones arranged therein and an outer area located on the outer side of the central area and having circular-arc zones arranged therein. The pitch of zones in a boundary area between the central area and the outer area and where the zone shape changes is smaller than a basic pitch which is the pitch of the circular and circular-arc zones in the central area and the outer area.
Claims7
A Fresnel lens having a plurality of concentrically-arranged circular and circular-arc zones formed on a surface of a base material thereof, comprising:
- a central area having part of the plurality of circular zones formed therein;
- an outer area located on an outer side of the central area and having part of the plurality of circular-arc zones formed therein;
- and
- a boundary area between the central area and the outer area and having part of the plurality of circular zones and part of the plurality of circular-arc zones formed therein, the boundary area including a boundary zone where a zone shape changes from a circular shape to a circular-arc shape,
- wherein the pitch of the zones in the boundary area is smaller than the pitch of the zones in the central area and the outer area.
2 more elements
Dependencies are inferred from the claim text.