Optical pickup

• US 20050141391A1
• Filed: 02/16/2005
• Published: 06/30/2005
• Est. Priority Date: 07/13/2000
• Status: Active Grant

• Current Assignee: Hiroshige Hirajima, Katsushige Masui, Keiji Sakai, Naotaka Otsuka, Noboru Fujita, Renzaburo Miki, Tetsuo Ueyama, Yukio Kurata
• Original Assignee: Hiroshige Hirajima, Katsushige Masui, Keiji Sakai, Naotaka Otsuka, Noboru Fujita, Renzaburo Miki, Tetsuo Ueyama, Yukio Kurata
• Inventors: Otsuka, Naotaka, Miki, Renzaburo, Hirajima, Hiroshige, Sakai, Keiji, Masui, Katsushige, Ueyama, Tetsuo, Kurata, Yukio, Fujita, Noboru
• Granted Patent: US 7,106,682 B2
• Time in Patent Office: Days
• US Class Current: 369/112.100
• CPC Class Codes: G11B 2007/0006 adapted for scanning different types of carrier, e.g. CD & DVD
• CPC Class Codes: G11B 7/0901 for track following only G11B7/0925, G11B7/094, G11B7/0941, G11B7/0943, G11B7/0945, G11B7/0946, G11B7/0948 take precedence
• CPC Class Codes: G11B 7/0903 Multi-beam tracking systems
• CPC Class Codes: G11B 7/0906 Differential phase difference systems
• CPC Class Codes: G11B 7/0908 for focusing only G11B7/0925, G11B7/094, G11B7/0941, G11B7/0943, G11B7/0945, G11B7/0946, G11B7/0948 take precedence
• CPC Class Codes: G11B 7/0916 Foucault or knife-edge methods
• CPC Class Codes: G11B 7/123 Integrated head arrangements, e.g. with source and detectors mounted on the same substrate
• CPC Class Codes: G11B 7/1275 Two or more lasers having different wavelengths
• CPC Class Codes: G11B 7/131 Arrangement of detectors in a multiple array
• CPC Class Codes: G11B 7/1353 Diffractive elements, e.g. holograms or gratings diffraction gratings per se G02B5/18; holograms per se G02B5/32; grating systems G02B27/44
• CPC Class Codes: G11B 7/1356 Double or multiple prisms, i.e. having two or more prisms in cooperation
• CPC Class Codes: G11B 7/1365 Separate or integrated refractive elements, e.g. wave plates
• CPC Class Codes: G11B 7/1381 Non-lens elements for altering the properties of the beam, e.g. knife edges, slits, filters or stops G11B7/1353 - G11B7/1369 take precedence
• CPC Class Codes: G11B 7/22 Apparatus or processes for the manufacture of optical heads, e.g. assembly

Abstract

An optical pickup can be provided, the optical pickup being capable of recording and playback of a plurality of optical disks having different specs by using light beams of different wavelengths, and further being suitable for integrating the semiconductor lasers and light receiving elements into a single package, by including: first and second semiconductor lasers adjacently disposed; a three-beam diffraction grating for generating three beams for tracking control; a second hologram element for diffracting light of the second semiconductor laser to guide it to a photosensor; a complex polarization beam splitter (PBS) for reflecting only light from the first semiconductor laser; and a first hologram element for diffracting light of the first semiconductor laser to guide it to the photosensor.

Claims

1. An optical pickup, comprising:

a first light source for generating a light beam having a first wavelength;

a second light source for generating a light beam having a second wavelength different from the first wavelength;

a lens system for focusing the two light beams on an optical disk;

a photosensor for sensing reflection light beams from the optical disk;

an optical path splitting element for splitting optical paths of the two reflection light beams having different wavelengths; and

first and second hologram elements for respectively diffracting at least one of the two light beams of the different wavelengths which were split by the optical path splitting element, and guiding the thus diffracted light to the shared photosensor,

wherein the first and second hologram elements are disposed in an optical path being a return travel path between the optical path splitting element and the photosensor through which only returning light travels.

2. The optical pickup set forth in claim 1, wherein the optical path splitting element is a polarization beam splitter.

13. The optical pickup set forth in claim 2, wherein the optical path splitting element is made up of a single polarization beam splitter for splitting the reflection light beams of two different wavelengths.

14. The optical pickup set forth in claim 13, wherein the polarization beam splitter has the same polarization characteristic with respect to the light beams of the first wavelength and the second wavelength.

15. The optical pickup set forth in claim 14, wherein the polarization beam splitter has such a characteristic as to transmit substantially full P polarized light and reflect substantially full S polarized, with respect to the light beams of the first wavelength and the second wavelength.

16. The optical pickup set forth in claim 15, further comprising a wave plate which is disposed in the optical path between the polarization beam splitter and the lens system so as to generate a ¼

wavelength phase difference with respect to the light beams of the first wavelength and the second wavelength.

17. The optical pickup set forth in claim 16, wherein the wave plate is integrally and fixedly bonded to an emission side of the polarization beam splitter.

18. The optical pickup set forth in claim 2, wherein the optical path splitting element is made up of a first polarization beam splitter for splitting the light beam of the first wavelength, and a second polarization beam splitter for splitting the light beam of the second wavelength.

19. The optical pickup set forth in claim 18, wherein the two polarization beam splitters respectively have different polarization characteristics with respect to a light beam of the first wavelength and a light beam of the second wavelength.

20. The optical pickup set forth in claim 19, wherein:

the first polarization beam splitter has such a characteristic as to transmit substantially full P polarized light and reflect substantially full S polarized light at least with respect to the light beam of the first wavelength, and

the second polarization beam splitter has such characteristics as to transmit substantially full P and S polarized light with respect to the light beam of the first wavelength, and transmit substantially full P polarized light and reflect substantially full S polarized light with respect to the light beam of the second wavelength.

21. The optical pickup set forth in claim 20, further comprising a wave plate which is disposed in the optical path between the polarization beam splitters and the lens system so as to generate a ¼

wavelength phase difference with respect to the light beams of the first wavelength and the second wavelength.

22. The optical pickup set forth in claim 21, wherein the wave plate is integrally and fixedly bonded to an emission side of the polarization beam splitter.

23. The optical pickup set forth in claim 2, wherein the first and second hologram elements are reflective holograms.

3-12. -12. (canceled)

24-29. -29. (canceled)

30. An optical pickup, comprising:

a first light source for generating a light beam having a first wavelength;

a second light source for generating a light beam having a second wavelength different from the first wavelength;

a lens system for focusing the two light beams on an optical disk;

a photosensor for sensing reflection light beams from the optical disk;

an optical path splitting element for splitting optical paths of the two reflection light beams having different wavelengths; and

first and second hologram elements for respectively diffracting at least one of the two light beams of the different wavelengths which were split by the optical path splitting element, and guiding the thus diffracted light to the shared photosensor,

wherein the optical path splitting element is one of the hologram elements for guiding the light beam of the first wavelength to the photosensor.

31. The optical pickup set forth in claim 30, further comprising a wavelength selecting diffraction grating for transmitting the substantially full light beam of the first wavelength and splitting the light beam of the second wavelength into three beams including 0th order light and ±

1st order light, the wavelength selecting diffraction grating being formed on a transparent substrate having the second hologram element formed thereon.

32. The optical pickup set forth in claim 30, wherein:

the first hologram element serving as the optical path splitting element splits the light beams of the first wavelength and the second wavelength in different directions, respectively, according to a different diffraction angle, and

the second hologram element diffracts the light beam of the second wavelength of the two beams split by the optical path splitting element, and transmits the light beam of the first wavelength.

33. The optical pickup set forth in claim 32, further comprising a wavelength selecting diffraction grating for transmitting the substantially full light beam of the first wavelength and splitting the light beam of the second wavelength into three beams including 0th order light and ±

1st order light, the wavelength selecting diffraction grating being formed on a transparent substrate having the second hologram element formed thereon.

34. The optical pickup set forth in claim 30, wherein a 2-division light receiving element is used to detect a focus error signal according to a single knife edge method from respective semicircular beams of either of the light beams of the first wavelength and the second wavelength, the semicircular beams being split by a split line in a direction corresponding to a direction of the radius of the optical disk.

35. The optical pickup set forth in claim 30, wherein:

the first hologram element is used to detect a tracking error signal according to a phase difference method or a push-pull method, and the second hologram element is used to detect a tracking error signal according to a three-beam method or a differential push-pull method.

36. The optical pickup set forth in claim 30, where the first light source is a semiconductor laser of a 650 nm band, and the second light source is a semiconductor laser of a 780 nm band.

37. The optical pickup set forth in claim 34, wherein at least one of the first and second light sources is a high-power laser so as to enable recording and playback with respect to the optical disk.

38-76. -76. (canceled)