Optical element, method of molding optical element, and mold

• US 20050094294A1
• Filed: 10/26/2004
• Published: 05/05/2005
• Est. Priority Date: 10/31/2003
• Status: Active Grant

• Current Assignee: Konica Minolta OPTO Incorporated (Konica Minolta Inc.)
• Original Assignee: Konica Minolta OPTO Incorporated (Konica Minolta Inc.)
• Inventors: Hattori, Hiroyuki, Wada, Kazuhiro
• Granted Patent: US 7,133,223 B2
• Time in Patent Office: Days
• US Class Current: 359/811
• CPC Class Codes: G02B 3/08 with discontinuous faces, e.g. Fresnel lens diffractive Fresnel lenses G02B5/1876
• CPC Class Codes: G02B 7/028 with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation

Abstract

This invention provides an optical element comprising: an optical functional section on a first surface of the optical element, the optical functional section having a fine structure; and a flange section formed on a periphery of the optical functional section, wherein the flange section has a heat shrinkage-inhibiting portion, which inhibits heat shrinkage of the optical element during molding in a direction perpendicular to an optical axis of the optical element. The invention further provides a method of molding the optical element, and a mold.

Claims

1. An optical element comprising:

an optical functional section on a first surface of the optical element, the optical functional section having a fine structure; and

a flange section formed around a periphery of the optical functional section,

wherein the flange section has a heat shrinkage-inhibiting portion, which inhibits heat shrinkage of the optical element during molding in a direction perpendicular to an optical axis of the optical element.

2. The optical element of claim 1, wherein the flange section has a structure in which the periphery of the optical functional section projects to a first surface side of the optical element in a direction of the optical axis of the optical element, and

wherein the heat shrinkage-inhibiting portion is an inner side surface of the flange section, and an angle formed by the heat shrinkage-inhibiting portion and the optical axis of the optical element is 0°

(inclusive) to 25°

(inclusive).

3. The optical element of claim 2, wherein the angle formed by the heat shrinkage-inhibiting portion and the optical axis of the optical element is 10°

(inclusive) to 20°

(inclusive).

4. The optical element of claim 1, wherein the optical element is molded with a mold including a first mold member, which forms the first surface of the optical element, and a second mold member, which forms a second surface opposite to the first surface, and

wherein the flange section has a structure so that F1 is larger than F2, where F1 is a separation force between the first mold member and the first surface and F2 is a separation force between the second mold member and the second surface.

5. The optical element of claim 4, wherein the flange section has a structure in which the periphery of the optical functional section projects to a first surface side of the optical element in a direction of the optical axis of the optical element, and

wherein an angle formed by an outer side surface of the flange section and the optical axis of the optical element is 0°

(inclusive) to 5°

(inclusive).

6. The optical element of claim 5, wherein the angle formed by the outer side surface of the flange section and the optical axis of the optical element is 0°

(inclusive) to 3°

(inclusive).

7. The optical element of claim 1, wherein the fine structure includes a ring-shape zone structure having a plurality of ring-shape zones, which are continuous through fine steps.

8. The optical element of claim 7, wherein the fine structure includes a ring-shape zone structure having a plurality of ring-shape zones, which are concentric of the optical axis of the optical element and are continuous through fine steps, and

wherein the ring-shape zone structure has a saw-toothed sectional shape.

9. The optical element of claim 7, wherein the fine structure includes a ring-shape zone structure having a plurality of ring-shape zones, which are concentric of the optical axis of the optical element and are continuous through fine steps, and

wherein the fine structure is a superposed ring-shape zone structure having stair-like steps on the respective ring-shape zones.

10. An optical element of claim 1, wherein the optical element has fine structures on the first surface of the optical element and a second surface, which is opposite to the first surface.

11. A method of molding an optical element, which includes an optical functional section on a first surface of the optical element and a flange section formed around a periphery of the optical functional section, the optical functional section having a fine structure, the method comprising the steps of:

filling a mold including a first mold member corresponding to the first surface of the optical element and a second mold member corresponding to a second surface opposite to the first surface, with a melted optical element material;

solidifying the filled optical element material;

opening the mold to separate the first mold member and the second mold member relatively apart from each other, wherein the solidified optical element material is left on the first mold member; and

releasing the optical element material from the first mold member by ejecting with an ejecting portion formed on a portion of the first mold member, the ejecting portion corresponding to the optical functional section of the optical element,

wherein the flange section of the optical element has a heat shrinkage-inhibiting portion, which inhibits heat shrinkage in a direction perpendicular to an optical axis of the optical element during at least one of the steps of solidifying, opening, and releasing.

12. A method of claim 11, wherein the flange section has a structure in which the periphery of the optical functional section projects to a first surface side of the optical element in a direction of the optical axis of the optical element, and

wherein the heat shrinkage-inhibiting portion is an inner side surface of the flange section, and an angle formed by the heat shrinkage-inhibiting portion and the optical axis of the optical element is 0°

(inclusive) to 25°

(inclusive).

13. A method of claim 12, wherein the angle formed by the heat shrinkage-inhibiting portion and the optical axis of the optical element is 10°

(inclusive) to 20°

(inclusive).

14. A method of claim 11, wherein the flange section has a structure so that F1 is larger than F2, where F1 is a separation force between the first mold member and the first surface and F2 is a separation force between the second mold member and the second surface.

15. A method of claim 14, wherein the flange section has a structure in which the periphery of the optical functional section projects to a first surface side of the optical element in a direction of the optical axis of the optical element, and

wherein an angle formed by an outer side surface of the flange section and the optical axis of the optical element is 0°

(inclusive) to 5°

(inclusive).

16. A method of claim 15, wherein the angle formed by the outer side surface of the flange section and the optical axis of the optical element is 0°

(inclusive) to 3°

(inclusive).

17. A method of claim 11, wherein the fine structure includes a ring-shape zone structure having a plurality of ring-shape zones, which are continuous through fine steps.

18. A method of claim 17, wherein the fine structure includes a ring-shape zone structure having a plurality of ring-shape zones, which are concentric of the optical axis of the optical element and are continuous through fine steps, and

wherein the ring-shape zone structure has a saw-toothed sectional shape.

19. A method of claim 17, wherein the fine structure includes a ring-shape zone structure having a plurality of ring-shape zones, which are concentric of the optical axis of the optical element and are continuous through fine steps, and

wherein the fine structure is a superposed ring-shape zone structure having stair-like steps on the respective ring-shape zones.

20. A method of claim 11, wherein the optical element has fine structures on the first surface of the optical element and a second surface, which is opposite to the first surface.

21. A mold for molding an optical element, which includes an optical functional section on a first surface of the optical element and a flange section formed around a periphery of the optical functional section, the optical functional section having a fine structure, the mold comprising:

a first mold member to form a first surface of the optical element, the first surface having the optical functional section; and

a second mold member which forms a second surface opposite to the first surface,

wherein the flange section has a heat shrinkage-inhibiting portion, which inhibits heat shrinkage during molding in a direction perpendicular to an optical axis of the optical element.

22. A mold of claim 21, wherein the flange section has a structure in which the periphery of the optical functional section projects to a first surface side of the optical element in a direction of the optical axis of the optical element, and

wherein the heat shrinkage-inhibiting portion is an inner side surface of the flange section, and an angle formed by the heat shrinkage-inhibiting portion and the optical axis of the optical element is 0°

(inclusive) to 25°

(inclusive).

23. A mold of claim 22, wherein the angle formed by the heat shrinkage-inhibiting portion and the optical axis of the optical element is 10°

(inclusive) to 20°

(inclusive).

24. A mold of claim 21, wherein the flange section has a structure so that F1 is larger than F2, where F1 is a separation force between the first mold member and the first surface and F2 is a separation force between the second mold member and the second surface.

25. A mold of claim 24, wherein the flange section has a structure in which the periphery of the optical functional section projects to a first surface side of the optical element in a direction of the optical axis of the optical element, and

wherein an angle formed by an outer side surface of the flange section and the optical axis of the optical element is 0°

(inclusive) to 5°

(inclusive).

26. A mold of claim 25, wherein the angle formed by the outer side surface of the flange section and the optical axis of the optical element is 0°

(inclusive) to 3°

(inclusive).

27. A mold of claim 21, wherein the fine structure includes a ring-shape zone structure having a plurality of ring-shape zones, which are continuous through fine steps.

28. A mold of claim 27, wherein the fine structure includes a ring-shape zone structure having a plurality of ring-shape zones, which are concentric of the optical axis of the optical element and are continuous through fine steps, and

wherein the ring-shape zone structure has a saw-toothed sectional shape.

29. A mold of claim 27, wherein the fine structure includes a ring-shape zone structure having a plurality of ring-shape zones, which are concentric of the optical axis of the optical element and are continuous through fine steps, and

wherein the fine structure is a superposed ring-shape zone structure having stair-like steps on the respective ring-shape zones.

30. A mold of claim 21, wherein the optical element has fine structures on the first surface of the optical element and a second surface, which is opposite to the first surface.