OPTICAL PICKUP AND OPTICAL INFORMATION PROCESSING DEVICE
First Claim
1. An optical pickup for performing at least one of recording, reproducing, and erasing of information for at least two types of optical information recording media, the optical pickup comprising:
- an optical focusing system configured to focus a light beam from a light source onto a first recording layer of a first optical information recording medium via a first substrate having a first thickness t1 with the use of a first numerical aperture NA1, and onto a second recording layer of a second optical information recording medium via a second substrate having a second thickness t2 that is different from the first thickness t1 with the use of a second numerical aperture NA2, wherein;
the optical focusing system comprisesan object lens designed to focus the light beam onto the first recording layer of the first optical information recording medium, andan aberration correction unit comprising at least one phase shifter surface that is divided into plural regions in a concentric manner according to steps having uneven shapes with different heights in a light axial direction, which phase shifter surface is configured to apply a phase difference to the light beam from the light source;
the plural regions comprise a center region comprising an optical axis, an outside annular region extending from a position of the first numerical aperture NA1 to a position of the second numerical aperture NA2, and a middle annular region positioned between the center region comprising the optical axis and the outside annular region;
phase differences of the center region, the outside annular region, and the middle annular region are integral multiples of 2π
with respect to a wavelength of the light beam;
the steps having the uneven shapes are formed in a first annular region between the center region and the middle annular region and in a second annular region between the middle annular region and the outside annular region; and
the steps are formed in such a manner as to reduce aberration that is caused by a difference between the first thickness t1 of the first substrate and the second thickness t2 of the second substrate.
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Accused Products
Abstract
A disclosed optical pickup includes an aberration correction unit with a phase shifter surface. On the phase shifter surface, rectangular or staircase-like steps are formed in a concentric manner around an optical axial center, in certain regions where a light beam passes through. The steps have different heights in the optical axial direction. A light beam having a wavelength of 405 nm is directly transmitted through the steps so that a phase difference is applied for correcting spherical aberration that occurs on a first optical recording medium. A light beam that passes through an annular region without any steps is focused on a second optical recording medium. A light beam that passes through an outside region is focused by an object lens on the second optical recording medium, and is not focused on the first optical recording medium.
13 Citations
13 Claims
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1. An optical pickup for performing at least one of recording, reproducing, and erasing of information for at least two types of optical information recording media, the optical pickup comprising:
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an optical focusing system configured to focus a light beam from a light source onto a first recording layer of a first optical information recording medium via a first substrate having a first thickness t1 with the use of a first numerical aperture NA1, and onto a second recording layer of a second optical information recording medium via a second substrate having a second thickness t2 that is different from the first thickness t1 with the use of a second numerical aperture NA2, wherein; the optical focusing system comprises an object lens designed to focus the light beam onto the first recording layer of the first optical information recording medium, and an aberration correction unit comprising at least one phase shifter surface that is divided into plural regions in a concentric manner according to steps having uneven shapes with different heights in a light axial direction, which phase shifter surface is configured to apply a phase difference to the light beam from the light source; the plural regions comprise a center region comprising an optical axis, an outside annular region extending from a position of the first numerical aperture NA1 to a position of the second numerical aperture NA2, and a middle annular region positioned between the center region comprising the optical axis and the outside annular region; phase differences of the center region, the outside annular region, and the middle annular region are integral multiples of 2π
with respect to a wavelength of the light beam;the steps having the uneven shapes are formed in a first annular region between the center region and the middle annular region and in a second annular region between the middle annular region and the outside annular region; and the steps are formed in such a manner as to reduce aberration that is caused by a difference between the first thickness t1 of the first substrate and the second thickness t2 of the second substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification