Optical device for making light converge

• US 6,791,755 B2
• Filed: 08/06/2002
• Issued: 09/14/2004
• Est. Priority Date: 08/08/2001
• Status: Expired due to Fees

• Current Assignee: Minolta Co., Ltd. (Konica Minolta Inc.)
• Original Assignee: Minolta Co., Ltd. (Konica Minolta Inc.)
• Inventors: Hatano, Hiroshi, Takada, Kyu
• Primary Examiner(s): Juba, Jr., John
• Application Number:
  US10/212,238
• Publication Number:
  US 20030039034A1
• Time in Patent Office: 770 Days
• Field of Search: 369/112.04, 369/44.24, 369/19, 369/565, 369/569, 369/572
• US Class Current: 359/565
• CPC Class Codes: G02B 27/4272 having plural diffractive elements positioned sequentially along the optical path
• CPC Class Codes: G02B 5/1819 Plural gratings positioned on the same surface, e.g. array of gratings plural diffractive elements positioned sequentially along the optical path G02B27/4272

Abstract

An optical device for making light converge produces a convergent light beam with a satisfactorily great numerical aperture and acceptably small aberrations. The optical device has a plurality of diffraction gratings that each make light converge. The light shone into the optical device is passed through one after another of those diffraction gratings in such a way that the light is made to converge to a higher degree every time it passes through one of the diffraction gratings. The diffraction gratings may be all transmissive, all reflective, or a combination of both. The diffraction gratings are formed on a surface of or at an interface inside the optical device, and two diffraction gratings may be formed on a single surface. The light is made to eventually converge on the exit surface of the optical device so that the optical device functions as a solid immersion device.

Claims

1. An optical device for making light shone into the optical device converge, comprising:

a plurality of diffracting portions each making light passing therethrough converge by diffraction, wherein

optical axes of the plurality of diffracting portions coincide with one another,

the light shone into the optical device is passed through one after another of the plurality of diffracting portions so that the light is made to converge to a higher degree every time the light passes through one of the diffracting portions, and

at least one of the diffracting portions makes light converge by reflecting the light.

2. The optical device as claimed in claim 1,

wherein at least one of the diffracting portions makes light converge by transmitting the light.

3. The optical device as claimed in claim 2, wherein

the plurality of diffracting portions are formed on a flat plate that includes a first surface on which the light is incident and a second surface located opposite to the first surface, a first diffracting portion being formed on the first surface and a second diffracting portion being formed on the second surface, the incident light being, in order, first transmitted through the first diffracting portion, then reflected from the second diffracting portion, and then reflected from the first surface so as to converge town the second surface.

4. The optical device as claimed in claim 2,

wherein the plurality of diffracting portions are formed on a flat plate that includes a first surface on which the light is incident and a second surface located opposite to the first surface, first and second diffracting portions being formed on the first surface, the incident light being, in order, first transmitted through the first diffracting portion, then reflected from the second surface, and then reflected from the second diffracting portion so as to converge toward the second surface.

5. The optical device as claimed in claim 1,

wherein at least one of the diffracting portions is formed on a surface of the optical device.

6. The optical device as claimed in claim 1,

wherein at least one of the diffracting portions is formed inside the optical device.

7. The optical device as claimed in claim 1,

wherein at least two of the diffracting portions are formed in different areas on a same surface.

8. The optical device as claimed in claim 1,

wherein at least one of the diffracting portions is a diffraction grating.

9. The optical device as claimed in claim 1,

wherein the light shone into the optical device is made to converge in such a way that the light has a minimum diameter on surface through which the light exits the optical device.

10. The optical device as claimed in claim 1, further comprising:

a light-shielding member provided on a surface through which the light shone into the optical device exits the optical device, the light-shielding member having an opening smaller than a diameter of the light on the surface,

wherein the light is made to exit the optical device through the opening.

11. The optical device as claimed in claim 1,

wherein part of a surface of the optical device is formed into a protruding portion, and the light shone into the optical device is made to exit the optical device through the protruding portion.

12. The optical device as claimed in claim 1, wherein

the plurality of diffracting portions are formed on a flat plate that includes a first surface on which the light is incident and a second surface located opposite to the first surface, first and second diffracting portions being formed on the second surface, the incident light being, in order, first transmitted through the first surface, then reflected from the first diffracting portion, then reflected from the first surface, then reflected from the second diffracting portion, and then reflected from the first surface, so as to converge toward the second surface.

13. A solid immersion device for use in an optical recording head that performs at least one of recording, reproducing, and erasing of information by use of light, comprising:

a plurality of diffracting portions each making light passing therethrough converge by diffraction, wherein

light shone into the solid immersion device is passed through one after another of the plurality of diffracting portions so that the light is made to converge to a higher degree every time the light passes through one of the diffracting portions, and

at least one of the diffracting portions makes light converge by reflecting the light.

14. The solid immersion device as claimed in claim 13,

wherein at least one of the diffracting portions makes light converge by transmitting the light.

15. The solid immersion device as claimed in claim 13,

wherein at least one of the diffracting portions is formed on a surface of the solid immersion device.

16. The solid immersion device as claimed in claim 13,

wherein at least one of the diffracting portions is formed inside the solid immersion device.

17. The solid immersion device as claimed in claim 13,

wherein the light shone into the solid immersion device is made to converge in such a way that the light has a minimum diameter on a surface through which the light exits the solid immersion device.

18. The solid immersion device as claimed in claim 13, further comprising:

a light-shielding member provided on a surface through which the light shone into the solid immersion device exits the solid immersion device, the light-shielding member having an opening smaller than a diameter of the light on the surface,

wherein the light is made to exit the solid immersion device through the opening.

19. The solid immersion device as claimed in claim 13,

wherein part of a surface of the solid immersion device is formed into a protruding portion, and the light shone into the solid immersion device is made to exit the solid immersion device through the protruding portion.

21. The solid immersion device as claimed in claim 13,

wherein at least one of the diffracting portions is a diffraction grating.

20. A solid immersion device for use in an optical recording head that performs at least one of recording, reproducing, and erasing of information by use of light, comprising:

a plurality of diffracting portions each making light passing therethrough converge by diffraction, wherein

light shone into the solid immersion device is passed through one after another of the plurality of diffracting portions so that the light is made to converge to a higher degree every time the light passes through one the diffracting portions, and

at least two of the diffracting portions are formed in different areas on a same surface.