Wide-angle variable focal length lens system

• US 7,359,124 B1
• Filed: 04/30/2005
• Issued: 04/15/2008
• Est. Priority Date: 04/30/2004
• Status: Expired due to Fees

• Current Assignee: Louisiana Tech University Foundation (Louisiana Tech University)
• Original Assignee: Louisiana Tech University Foundation Incorporated
• Inventors: Gunasekaran, R. Alfred, Fang, Ji, Wang, Weisong, Agarwal, Mangilal, Chen, Jackie, Varahramyan, Kody
• Primary Examiner(s): SCHWARTZ, JORDAN MARC
• Application Number:
  US11/119,517
• Time in Patent Office: 1,081 Days
• Field of Search: 359/665, 359/666
• US Class Current: 359/666
• CPC Class Codes: G02B 1/06 made of fluids in transparent cells
• CPC Class Codes: G02B 15/00 Optical objectives with means for varying the magnification anamorphotic objectives G02B13/08
• CPC Class Codes: G02B 3/14 of variable focal length

Abstract

A variable focal length microlens system having a base section with a fluid chamber and a fluid pressurization mechanism. A flexible, substantially transparent polymer lens section is fixed above the fluid chamber and the lens section has a curvature providing an initial focal point when in an unstrained state. The fluid chamber is substantially sealed and the fluid pressurization mechanism includes a flexible wall in the base section. The flexible wall may be displaced by magnetic activation, PZT activation of another activating mechanism.

Claims

1. A variable focal length microlens apparatus comprising:

a. a base section having a fluid chamber and a fluid pressurization mechanism; and

b. a flexible, substantially transparent polymer lens section fixed above said fluid chamber, said lens section having a curvature providing an initial focal point when in an unstrained state; and

c. wherein said apparatus has a focal length range which can vary between about 1.5 mm and about 16 mm.

2. The variable focal length microlens apparatus of claim 1, wherein said lens section has a contact angle of at least ten degrees in an unstrained state.

3. The variable focal length microlens apparatus of claim 1, wherein said base section is formed of a polymer and said base section and lens section are joined to a silicon intermediate substrate.

4. The variable focal length microlens apparatus of claim 3, wherein said lens section is formed substantially of a PDMS material.

5. The variable focal length microlens apparatus of claim 1, wherein said lens section comprises a convex lens surface and said convex lens surface has a base diameter of between about 100 um and about 3000 um.

6. The variable focal length microlens apparatus of claim 5, wherein said convex lens surface has a height of between about 15 um and about 200 um in said unstrained state.

7. The variable focal length microlens apparatus of claim 1, wherein said fluid pressurization mechanism comprises a fluid channel connecting said fluid chamber to an exterior of said base section.

8. The variable focal length microlens apparatus of claim 7, wherein said fluid channel is connected to a fluid pump exterior to said base section.

9. The variable focal length microlens apparatus of claim 1, wherein said fluid chamber is substantially sealed and said fluid pressurization mechanism comprises said base section having a flexible wall.

10. The variable focal length microlens apparatus of claim 9, wherein said flexible wall is displaced by a magnetic activation mechanism in order to increase the pressure of a fluid within said fluid chamber.

11. The variable focal length microlens apparatus of claim 10, wherein said magnetic activation mechanism comprises said flexible wall having a magnetic material incorporated therein or affixed thereto and said base section includes a magnet for urging displacement of said magnetic material.

12. The variable focal length microlens apparatus of claim 11, wherein said magnet is an electro-magnet.

13. The variable focal length microlens apparatus of claim 9, wherein said flexible wall is displaced by a PZT material acting thereon.

14. The variable focal length microlens apparatus of claim 13, wherein said PZT material is attached to said flexible wall.

19. The variable focal length microlens apparatus of claim 1, wherein said polymer lens section is formed by a method comprising the steps of:

a. using a lithography process to form a lens base of a thermally reflowable first material;

b. heating said reflowable first material to form a convex mother lens;

c. transferring the shape of said mother lens to a mold master of a second material;

d. coating a substantially transparent polymer lens material onto said mold master; and

e. releasing said transparent polymer lens material from said mold master.

15. A variable focal length microlens apparatus comprising:

a. a base section having a fluid chamber and a fluid pressurization mechanism;

b. a flexible, substantially transparent polymer lens section fixed above said fluid chamber said lens section having a curvature providing an initial focal point when in an unstrained state;

c. wherein said fluid chamber is substantially sealed and said fluid pressurization mechanism comprises a thermo-expansive liquid and a heating element positioned in contact with said thermo-expansive liquid; and

d. wherein a temperature sensor is positioned in contact with said liquid.

16. The variable focal length microlens apparatus of claim 15, wherein said liquid has a thermal expansion coefficient of between about 0.0002 and about 0.002°

C.<sup>−

1</sup>.

17. The variable focal length microlens apparatus of claim 16, wherein said temperature sensor comprises a conductive metal trace applied to a bottom wall of said fluid chamber.

18. The variable focal length microlens apparatus of claim 15, wherein said heating element is a metal strip applied to a bottom wall of said fluid chamber.

20. The variable focal length microlens apparatus of claim 15, wherein said apparatus has a focal length range which can vary between about 1.5 mm and about 16 mm.

21. The variable focal length microlens apparatus of claim 20, wherein said lens section comprises a convex lens surface and said convex lens surface has a base diameter of between about 100 um and about 3000 um.