Sharp Kabushiki Kaisha Corporation

Toshiya Nagahama

Yukio Kurata

Yoshio Yoshida

Katsushige Masui

Kazuhiro Tsuchida

Keiji Sakai

Tetsuo Ueyama

Shigehiro Yamada

Yasuo Nakata

Naruichi Yokogawa

Kazunori Matsubara

Masahiro Ikehara

Naotaka Otsuka

Takahide Ishiguro

Koji Yoshifusa

Yasushi Seike

Naotaka Ohtsuka

An object of the invention is to provide a splitter, a light emitter, and an optical pickup apparatus which can realize a stable track servo. Because of the structure of an optical system including an objective lens () and a hologram pattern (), even when the hologram pattern () is irradiated with a reflected light from one recording layer other than another recording layer in a focused state, first and second TES splitting portions () are not irradiated with the reflected light from the one recording layer, but the reflected light is led to an axis vicinity portion () only. Accordingly, light reception by first and second TES light receiving portions () is prevented, accurate track position information and deviation information can be positively acquired, and troubles such as the objective lens () being driven beyond a movable range can be eliminated.

Splitting element, light emitter, and optical pickup apparatus

To read information from a target information recording surface reliably by canceling DC offsets in tracking-signal detection signals is provided. In effecting tracking servo by 3-beam method, auxiliary light receiving domains D, D, D, Dare provided. The auxiliary light receiving domain receives images formed by the light returned from a different information recording surface from the one targeted for reading. Sub beams of &#xb1; first-order diffracted light enter the light receiving domains D, D, D, D. With respect to the diffraction direction of the hologram, the auxiliary light receiving domains D, D(D, D) are provided on both sides of the light receiving domain D(D). Since signals are computed as: D&#x2212;(D+D); and D&#x2212;(D+D) with the internal connection, DC offsets can be canceled in RES signals (D+D, D+D) used in the DPP method.

Optical pickup device using polarizing hologram element and hologram laser therefor

Not only a semiconductor laser element and a photodetector but also a capacitor connected to the photodetector is housed in a package to thereby reduce the distance from the capacitor to the photodetector so that power source noise is efficiently suppressed by the capacitor and a power source noise suppression effect is improved.

Semiconductor laser device and method for producing the same

An optical pickup apparatus for reproducing information from an optical recording medium such as a compact disc comprising: a laser device; one or more diffraction devices; and a photodetector receiving a laser beam diffracted by the diffraction device. The surfaces of the diffraction device are provided with an antireflection coating. When the apparatus is used for the three-beam method, the two photodetecting areas in the photodetector for producing the tracking error signal are different in size and in positional relation to the laser device.

Optical pickup apparatus

An optical pickup using a holographic optical element includes a light source, a lens system for converting an optical beam outputted from the light source onto a recording carrier, a photodetector for detecting reflected light from the recording carrier and a diffraction grating for introducing the reflected light from the recording carrier to the photodetector in a light path connecting the recording carrier and the light receiving element. The photodetector includes a photodiode and a signal processing circuit which at least amplifies the output signal of the photodiode.

Optical pickup device using a holographic optical element and an

An optical pick-up device for focusing a laser beam emitted from a light emitting element through an optical system onto a recording medium. The beam is reflected from the recording medium and redirected through the same optical system on to a photodetector. A tracking error signal and a focusing error signal are produced from the output signals of the photo-detector. A diffracting element positioned before the light emitting element and the photo-detector and produces two sub-spots in two directions for applying the so-called 3-spots method from the laser beams that were projected from the light emitting element toward the recording medium. The diffracting element is divided into a first sub-region and a second sub-region formed in the same place and defined by a parting line aligned substantially perpendicular to the track direction. The first sub-region includes a diffraction grating for diffracting three beams that comprise a main beam toward the recording medium. The second sub-region includes a diffraction grating for diffracting the reflected beams of the three beams from the recording medium in the direction where the photo-detecting element is installed.

Optical pick-up device using diffraction grating element having two

An optical pickup device in which a main beam and a pair of sub-beams are used and a diffraction device is disposed between a recording medium and a light receiving device such as a photodetector is disclosed. The diffraction device comprises first to third diffraction regions. The second and third regions receive light beams from the recording medium which are substantially identical in amount to each other. The light receiving device comprises a first to a fourth light receiving regions. The first and second light receiving regions are juxtaposed, and separated by a line. The main beam which has been diffracted by the first diffraction region is focused onto said line. The main beam which has been diffracted by the second diffraction region is focused onto the first light receiving region. The main beam which has been diffracted by the third diffracting region is focused onto the second light receiving region. The sub-beams which have been diffracted by the diffraction device are focused onto the third and fourth light receiving regions, respectively. Alternatively, the diffraction device comprises an area where one or more diffraction regions are formed. The farthest point of the area at the side of the light receiving device is separated from the optical axis by a predetermined distance, to prevent the first order diffracted beam from entering the optical system disposed between the diffraction device and a recording medium.

Optical pickup device with diffraction device

An optical pickup device includes a light source, an optical lens system that converges light beams from the light source onto a recording medium, a photodetector with three divided regions that detects light beams reflected from the recording medium, and a hologram optical element that introduces the reflected light beams from the recording medium into the photodetector. The hologram optical element is divided into two regions, a part of the reflected light beams from the recording medium is diffracted by the first region of the hologram optical element and focused on a division line in the direction of the diffraction of the hologram optical element. The division line divides the photodetector into two regions, the first region and the second region. The other part of the reflected light beams is diffracted by the second region of the hologram optical element and focused on the third region of the photodetector. A difference in the output intensity between the first and second regions of the photodetector results in a focus error signal and the total of the output intensity of the first, second and third regions of the photodetector results in an information signal.

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Nara, Japan

Toshiya Nagahama