Optical pick-up apparatus
AssigneeRicoh Company, Ltd.
InventorYoshitaka Takahashi
Life of this patent
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Abstract
The present invention provides a method and apparatus for utilizing light rays of differing wavelengths to read optical discs of different respective capacities. The present invention serves to prevent aberration of the minute optical spot used to read the respective optical discs and also serves to eliminate an offset component with respect to the signals received by the photo detector, as reflected from the respective optical discs.
Claims36
A system for use with optical disk reproduction, the system comprising:
- a beam shaping prism, a light entry portion of said beam shaping prism being located at a convergence point of first and second light rays received from each of at least first and second light sources, said first light source producing light rays of a first wavelength, said second light source producing light rays of a second wavelength, said second wavelength being greater than said first wavelength, wherein
- an angle with which said light rays of said first wavelength are incident to said beam shaping prism is greater than an angle with which said light rays of said second wavelength are incident to said beam shaping prism, and wherein
- respective angles of said first and second light rays are nearly equal upon said light rays exiting said beam shaping prism.
A method of reproducing an optical disc, the method comprising:
- receiving light rays from a plurality of light sources at a beam shaping prism, a first one of said plurality of light sources producing light rays of a first wavelength, a second one of said plurality of light sources producing light rays of a second wavelength, said second wavelength being greater than said first wavelength;
- passing said first and second light rays through a beam shaping prism, a light entry portion of said beam shaping prism being located at a convergence point of said first and second light rays, wherein
- an angle with which said light rays of said first wavelength are incident to said beam shaping prism is greater than an angle with which said light rays of said second wavelength are incident to said beam shaping prism, and wherein
- respective angles of said first and second light rays are nearly equal upon said light rays exiting said beam shaping means.
A beam shaping prism for use with optical disk reproduction, said beam shaping prism comprising:
- a light entry portion for being positioned at a convergence point of first and second light rays received from each of at least first and second light sources, said first light source producing light rays of a first wavelength, said second light source producing light rays of a second wavelength, said second wavelength being greater than said first wavelength;
- and
- a light exiting portion, wherein respective angles of said first and second light rays are nearly equal upon said light rays exiting said beam shaping prism when an angle with which said light rays of said first wavelength are incident to said light entry portion is greater than an angle with which said light rays of said second wavelength are incident to said light entry portion.
A beam shaping prism for use with optical disk reproduction, said beam shaping prism comprising:
- a light entry portion for being positioned at a predetermined distance beyond a convergence point of first and second light rays received from each of at least first and second light sources, said first light source producing light rays of a first wavelength, said second light source producing light rays of a second wavelength, said second wavelength being greater than said first wavelength;
- and
- a light exiting portion, wherein respective angles of said first and second light rays are nearly equal upon said light rays exiting said beam shaping prism when an angle with which said light rays of said first wavelength are incident to said light entry portion is greater than an angle with which said light rays of said second wavelength are incident to said light entry portion.
Dependencies are inferred from the claim text.