Method for fabricating aspherical lens

• US 20040247692A1
• Filed: 06/03/2004
• Published: 12/09/2004
• Est. Priority Date: 06/03/2003
• Status: Abandoned Application

• Current Assignee: Hon Hai Precision Industry Co., Ltd.
• Original Assignee: Hon Hai Precision Industry Co., Ltd.
• Inventors: Chen, Ga-lane
• Application Number:
  US10/861,020
• Publication Number:
  US 20040247692A1
• Time in Patent Office: Days
• US Class Current: 424/501
• CPC Class Codes: G02B 27/4216 correcting geometrical aberrations
• CPC Class Codes: G02B 5/1814 structurally combined with one or more further optical elements, e.g. lenses, mirrors, prisms or other diffraction gratings G02B5/189 takes precedence
• CPC Class Codes: G03F 7/0005 Production of optical devices or components in so far as characterised by the lithographic processes or materials used therefor

Abstract

A method for fabricating an aspherical lens includes the steps of: providing an aspherical lens (10, 10′) having an aspherical surface (101, 101′) and an opposite flat surface (102, 102′); and defining a multiple-step grating in the flat surface by a photolithographic method. The aspherical lens has a reduced chromatic aberration effect, and can thus provide a clear image. Furthermore, an effect of the aspherical lens having the grating is equivalent to that of a conventional aspherical lens unit. Thus when the aspherical lens is used in an optical system, it can reduce a bulk and a weight of the optical system.

Claims

1. A method for fabricating an aspherical lens, comprising the steps of:

(a) providing an aspherical lens, the aspherical lens having an aspherical surface and an opposite flat surface; and

(b) defining a multiple-step grating in the flat surface.

2. The method as claimed in claim 1, wherein step (b) comprises the steps of:

(b1) forming a photoresist film on the flat surface;

(b2) placing a mask on the photoresist film, a resolution of the mask being R;

(b3) forming a grating with a set of steps in the flat surface by first exposure, developing and etching processes; and

(b4) repeating the exposure, developing and etching processes n times, each time using a mask having a resolution of (2ⁿ)*(R), wherein n is a positive integer, whereby a corresponding 2ⁿ⁺¹-step grating is obtained.

3. The method as claimed in claim 2, wherein each exposure process is an ultraviolet radiation exposure process executed by an aligner or a stepper.

4. The method as claimed in claim 2, wherein each exposure process is executed by an electron beam writer.

5. The method as claimed in claim 2, wherein each etching process is executed by using a photo etching technology or a μ

-ray developing technology.

6. The method as claimed in claim 2, wherein a depth of recesses produced in each etching process is approximately half that of recesses produced in an immediately preceding etching process.

7. The method as claimed in claim 2, wherein R is approximately 100 lines/mm.

8. The aspherical lens made from the method as claimed in claim 1.

9. A method for fabricating an aspherical lens, comprising the steps of:

(a) providing an aspherical lens, the aspherical lens having an aspherical surface and an opposite flat surface; and

(b) defining a symmetrical multiple-step grating in the flat surface.

10. The method as claimed in claim 9, wherein step (b) comprises the steps of:

(b1) forming a photo resist film on the flat surface;

(b2) placing a mask on the photo resist film, a resolution of the mask being R;

(b3) forming a grating with a set of steps in the flat surface by first exposure, developing and etching processes; and

(b4) repeating the exposure, developing and etching processes once, using a mask having a resolution of 3R, whereby a corresponding 4-step grating is obtained.

11. The method as claimed in claim 10, wherein each exposure process is an ultraviolet radiation exposure process executed by an aligner or a stepper.

12. The method as claimed in claim 10, wherein each exposure process is executed by an electron beam writer.

13. The method as claimed in claim 10, wherein each etching process is executed by using a photo etching technology or a μ

-ray developing technology.

14. The method as claimed in claim 10, wherein a depth of recesses produced in the repeated etching process is approximately half that of recesses produced in the first etching process.

15. The method as claimed in claim 10, wherein R is approximately 100 lines/mm.

16. The aspherical lens made from the method as claimed in claim 9.

17. A method of making a lens comprising steps of:

a. providing a lens including a curved surface and a flat surface opposite to each other;

b. forming a multi-step configuration on the flat surface in cycle.

18. The method as claimed in claim 17, wherein step (b) includes:

b1. applying a patterned photoresist film on the flat surface with some specific pattern exposing some portions of the lens without protection of the photoresist film;

b2 etching said some portions;

b3. removing the patterned photoresisit film and forming corresponding multi-step thereof accordingly.

19. The method as claimed in claim 18, wherein said step (b1) includes:

b11. applying a full un-patterned photoresisit film on the flat surface;

b12. applying a mask on the photoresisit film wherein said mask defines said specific pattern; and

b13. removing portions of the photoresist film via an exposure process according to said specific pattern.

20. The method as claimed in claim 17, wherein step (b) is repeated under a condition that the patterns of the photoresisit films become finer and finer so as to form more finer multi-step configurations thereof accordingly.