Design and fabrication process for a lens system optically coupled to an image-capture device

• US 6,747,805 B2
• Filed: 07/22/2002
• Issued: 06/08/2004
• Est. Priority Date: 07/20/2001
• Status: Expired due to Fees

• Current Assignee: Michel Sayag
• Original Assignee: Michel Sayag
• Inventors: Sayag, Michel
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): Harrington, Alicia M.
• Application Number:
  US10/202,454
• Publication Number:
  US 20030016452A1
• Time in Patent Office: 687 Days
• Field of Search: 359/620, 359/664, 359/710, 359/715, 359/717, 359/738, 359/797, 359/793, 359/794, 359/795, 359/796, 359/798, 348/335, 348/340
• US Class Current: 359/664
• CPC Class Codes: G02B 13/005 having spherical lenses only
• CPC Class Codes: G02B 13/0055 employing a special optical element
• CPC Class Codes: G02B 13/24 for reproducing or copying at short object distances
• CPC Class Codes: G02B 7/027 the lens being in the form of a sphere or ball
• CPC Class Codes: G02B 9/06 two + components
• CPC Class Codes: H04N 23/55 Optical parts specially adapted for electronic image sensors; Mounting thereof

Abstract

Simple, inexpensive and durable multi-element lens systems are provided. These lens systems may be optically coupled to digital image-capturing devices, such as those used in digital cameras. Some lens systems of the present invention include a glass microsphere bonded to a planar surface of a glass hemisphere. In preferred lens systems, the thickness of the glass hemisphere is selected to form an image plane for transmitted light that is tangent to the surface of the microsphere. Accordingly, in digital cameras fabricated with such lens systems, the glass microsphere can be attached directly to a digital image-capturing device. These preferred lens systems require no focusing adjustment and are suitable for applications to requiring a wide field of view. In some embodiments, the glass microsphere is bonded to the glass hemisphere using a light-absorbing material in order to create an apodized pupil. Some such embodiments are fabricated with a light-absorbing material with an absorption coefficient that varies according to the wavelength of transmitted light.

Claims

1. An optical system, comprising:

a digital image-capture device; and

a lens system coupled to the digital image-capture device, the lens system comprising;

a first lens which is approximately spherical in shape and is coupled to the digital image-capture device by a first bonding material; and

a second lens comprising a convex surface and a substantially planar surface, wherein at least a portion of the substantially planar surface is coupled to the first lens by a second bonding material.

2. The optical system of claim 1, wherein the first lens is in direct contact with the digital image-capture device.

3. The optical system of claim 1, wherein the substantially planar surface is in direct contact with the first lens.

4. The optical system of claim 1, wherein a thickness of the second lens is selected to cause light transmitted by the lens system to focus on the digital image-capture device.

5. The optical system of claim 1, wherein a thickness of the second lens is selected to cause a paraxial focal point of light transmitted by the lens system to be positioned proximate a surface of the first lens.

6. The optical system of claim 1, wherein the second lens is approximately hemispherical in shape.

7. The optical system of claim 1, wherein the first lens is formed of a material selected from the group consisting of true glass, quartz, rutile, ruby and fused silica.

8. The optical system of claim 1, wherein the second lens is formed of a material selected from the group consisting of true glass, quartz, rutile, ruby and fused silica.

9. The optical system of claim 1, wherein the first bonding material is substantially transparent.

10. The optical system of claim 1, wherein the second bonding material is substantially transparent.

11. The optical system of claim 1, wherein:

the first lens has a first index of refraction;

the second lens has a second index of refraction;

the first bonding material has a third index of refraction; and

the second bonding material has a fourth index of refraction; and

wherein the first and second indices of refraction are each less than either of the third or fourth indices of refraction.

12. The optical system of claim 1, wherein the second bonding material comprises a light-absorbing material.

13. The optical system of claim 1, wherein the lens system further comprises a spacer disposed between the first lens and the digital image-capture device, wherein the spacer causes light transmitted by the lens system to focus on the digital image-capture device.

14. The optical system of claim 5, wherein the first lens has a first radius and the second lens has a second radius, and wherein the first radius is approximately equal to the second radius.

15. The optical system of claim 5, wherein the first lens has a first diameter and the second lens has a second diameter, and wherein the first diameter is approximately twice the second diameter.

16. The optical system of claim 12, wherein the second bonding material creates an apodized pupil.

17. The optical system of claim 12, wherein the lens system further comprises a lens barrel within which at least portions of the first lens and the second lens are disposed, and wherein the second bonding material occupies substantially all of a volume defined by the first lens, the substantially planar surface and the lens barrel.

18. The optical system of claim 12, wherein the light-absorbing material has an absorption coefficient that varies for different wavelengths of light.

19. The optical system of claim 13, wherein a thickness of the spacer is approximately half of a diameter of the first lens.

20. A method of forming an optical system, the method comprising:

a first bonding step of attaching a first glass lens which is approximately spherical in shape to a substantially planar surface of a second glass lens, wherein the second glass lens comprises a convex surface and the substantially planar surface; and

a second bonding step of attaching the first glass lens to a digital image-capture device.

21. The method of claim 20, wherein the first bonding step comprises the step of placing the substantially planar surface in direct contact with the first glass lens.

22. The method of claim 20, wherein the second bonding step comprises the step of placing the first glass lens in direct contact with the digital image-capture device.

23. The method of claim 20, further comprising the step of selecting a thickness of the second glass lens to cause light transmitted by the first glass lens and the second glass lens to focus on the digital image-capture device.

24. The method of claim 20, further comprising the step of selecting a thickness of the second glass lens to cause a paraxial focal point of light transmitted by the first glass lens and the second glass lens to be positioned proximate a surface of the first glass lens.

25. The method of claim 20, wherein the second glass lens is approximately hemispherical in shape.

26. The method of claim 20, wherein the first bonding step comprises bonding the substantially planar surface to the first lens using a light-absorbing bonding material, thereby creating an apodized pupil for light transmitted by the optical system.

27. The method of claim 20, further comprising the step of forming the second glass lens by grinding down a substantially spherical lens.

28. The method of claim 20, further comprising the step of forming the first glass lens by a tumbling process.

29. The method of claim 26, wherein the first bonding step further comprises the steps of:

disposing at least a portion of the first lens and a portion of the second lens within a lens barrel; and

disposing the light-absorbing bonding material within substantially all of a volume defined by the first lens, the substantially planar surface and the lens barrel.

30. An apodization filter, comprising:

a plano-plano element having a first index of refraction;

a plano-convex element comprising a convex surface and a substantially planar surface, wherein the convex surface is disposed proximate the plano-plano element; and

a light-absorbing bonding material disposed within a volume defined by the convex surface and the plano-plano element, wherein the light-absorbing bonding material creates an apodized pupil for light transmitted through the apodization filter.

31. The apodization filter of claim 30, wherein a transmission T of light varies along a radius x of the plano-convex element substantially as T=exp (−

α

x²), where α

is an absorption coefficient of the light-absorbing bonding material.

32. The apodization filter of claim 30, wherein the plano-convex element is truncated.