Pioneer Corporation

Tomotaka Nishimura

Hitoshi Furuhata

Akira Miura

Masayuki Koyama

Taichi Akiba

Nobuo Ishida

Hirokatsu Nagatake

An optical pickup which appropriately detects reflected light and return light reflected back from an information recording medium even if a laser light Bemitted from a light source varies in wavelength. The transmittances of a half mirror to the laser light Bemitted from the light source, and to the reflected light Bwr, Ber or the return light Brr reflected back from the information recording medium are preset according to a predetermined condition, i.e., Tpc(&#x3bb;c)/Tp(&#x3bb;)=(1&#x2212;Ts(&#x3bb;)/(1&#x2212;Tsc(&#x3bb;c))&#xd7;(Tsc(&#x3bb;c)/Ts(&#x3bb;)). Here, &#x3bb; is a predetermined wavelength emitted from a semiconductor laser as the light source, Ts(&#x3bb;) is a transmittance to the laser light Bwith a predetermined polarization, Tp(&#x3bb;) is a transmittance to the reflected light Bwr, Ber or the return light Brr reflected back from the information recording medium when the laser light Bwith the predetermined wavelength &#x3bb; is emitted, Tsc(&#x3bb;c) is a transmittance to the laser light Bwith a wavelength &#x3bb;c when the semiconductor laser varies in wavelength characteristic, and Tpc(&#x3bb;c) is a transmittance to the reflected light Bwr, Ber or the return light Brr reflected back from the information recording medium when the laser light Bwith the wavelength &#x3bb;c is emitted.

Optical pickup

An optical pickup apparatus comprises a first light source for emitting a first laser beam having a first wavelength; a second light source for emitting a second laser beam having a second wavelength; and an objective lens for condensing the first laser beam and the second laser beam. The first light source and the second light source are disposed in positions in such a way that a total amount of coma aberration, which is generated on the first laser beam in accordance with a distance between the first light source and an optical axis of a whole optical system and coma aberration, which is generated on the first laser beam in accordance with a tilting amount of the objective lens becomes null, and a total amount of coma aberration, which is generated on the second laser beam in accordance with a distance between the second light source and said optical axis and coma aberration, which is generated on the second laser beam in accordance with the tilting amount of the objective lens becomes null.

Optical pickup apparatus

An optical pickup apparatus has a simplified configuration for using a plurality of laser beams at different wavelength to reduce the size, and a laser diode chip for use therewith. An irradiation light path for leading a laser beam emitted from a light emitter to a recording medium is provided with an optical axis correcting element for passing a first laser beam and for diffracting a second laser beam having a wavelength different from that of the first laser beam to generate diffracted light which has the optical axis substantially matching the optical axis of the first laser beam. The optical axis correcting element is arranged at a position at which the center of a light intensity distribution of the first laser beam incident thereto matches the center of a light intensity distribution of the second laser beam incident thereto.

Optical pickup apparatus an optical axis correcting element

An optical pickup apparatus which, assuming that a distance from a first light source to a first grating is a, a distance from a second light source to a second grating is b, a first predetermined grating pitch is I, a second predetermined grating pitch is J, the wavelength of a first laser beam is &lgr; , and the wavelength of a second laser beam is &lgr; , satisfies &lgr; >(I&middot;b)/(J&middot;a), and which is capable of preventing a drop in the level of a tracking error signal resulting from decentering of an optical recording medium, even in the case of using either of optical recording media of different recording densities.

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Tokorozawa, Japan

Tomotaka Nishimura