Modified light-receiving element in an optical pickup for reading optical discs
AssigneeRohm Co., Ltd.
InventorsNaotaro Nakata, Takeshi Yamamoto
Life of this patent
Estimating the term…
Abstract
An optical pickup includes a photo-detector. The photo-detector is structured by light receiving elements on one of which a blind zone is formed. If a relationship between an output of the light receiving element formed with a blind zone and a lens position is displayed as a graph on a measurement signal output device, a point that a beam converges on the blind zone, i.e., a point that a spot size assumes a minimum, is displayed as an edge. In the photo-detector, a region for receiving a sub-beam on light shield side, i.e., one sub-beam having a grater spot size, has a width broader than a width of a region for receiving a sub-beam on an aperture side, i.e., another sub-beam smaller in spot size.
Claims13
An optical pickup, comprising:
- a laser element for emitting laser light;
- a lens for causing the laser light to converge on a disc;
- a diffraction element having first and second region each of which diffracts reflection light from said disc;
- a photo-detector for receiving the reflection light traveled through said diffraction element, said photo-detector includes a first light receiving element on which the reflection light diffracted by said first region converges, a second light receiving element on which the reflection light diffracted by said second region converges and a third light receiving element, said second light receiving element and said third light receiving element being separated by a divisional line extending almost in a same direction as a direction of diffraction by the second region;
- and
- a blind zone for dividing a light receiving surface of said first light receiving element into two.
An optical pickup, comprising:
- a splitting element which splits a laser beam from a laser element into one main beam and two sub-beams;
- a lens for causing the main beam and the sub-beams to converge on a disc;
- a diffraction element divided into first and second regions to diffract reflection light from said disc;
- a photo-detector for receiving the reflection light traveled through said diffraction element, said photo-detector including first and second light receiving portions for respectively receiving the main beam and the sub-beams diffracted by said first region and said second region;
- said second light receiving portion being broader in width at a light shield side region, said light shield side region for receiving the sub-beam diffracted from a light shield side of said diffraction element, than a width at an aperture side region, said aperture side region for receiving the sub-beam diffracted from an aperture side of said diffraction element.
Dependencies are inferred from the claim text.