Sanyo Electric Co., Ltd.

Minoru Sawada

Kazushi Mori

Atsushi Tajiri

Yasuaki Inoue

Takenori Goto

Akira Ibaraki

Yasoo Harada

Daisuke Ide

Masayuki Shono

Shigeharu Matsushita

Mitsuaki Matsumoto

Koji Tominaga

Kohji Matsumura

Daijiro Inoue

Seiichi Banba

Toyozo Nishida

Emi Fujii

Yasuhiro Ueda

Satoshi Terada

Daijirou Inoue

In a holographic pattern provided in a holographic optical element, a patterntwists a diffracted light beam in a clockwise direction, to form a semi-circular light spot Sa on photodetection parts A and B so as to extend over a dividing line LX in a four-segment photodetection part. A patternsimilarly twists the diffracted light beam in a clockwise direction, to form a semi-circular light spot Sb on photodetection parts C and D so as to extend over a dividing line LX in the four-segment photodetection part.

Holographic optical element, position shift detecting apparatus, optical pickup apparatus, optical recording medium drive and method of fabricating holographic optical element

A six-segment holographic surface is divided into regions by dividing lines. A four-segment photodetection part is divided into four photodetection parts equal in area by a section line substantially parallel to the radial direction of an optical disk and a section line orthogonal thereto. A main light beam diffracted in the regions of the six-segment holographic surface are condensed as spots at positions apart from each other on opposite sides on a section line of the four photodetection parts, and the main beam diffracted in the regions is condensed as spots in the center of the photodetection parts of the four-segment photodetection part.

Optical pickup with a diffraction element consist of six regions providing spatial variation corresponding to a focas state

A grating surface of a diffraction grating diffracts a laser beam emitted from a semiconductor laser device in &plusmn;1st order directions. The grating surface is formed in a rectangular or elliptic shape in such dimensions that a light spot formed on an objective lens by &plusmn;1st order diffracted beams is located in an aperture of the objective lens and not displaced from the aperture even if the objective lens is horizontally moved in a tracking operation. A grating surface of another diffraction grating has a width smaller than the width of an overlap region of a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the &plusmn;1st direction, entering an objective lens and a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the &minus;1st direction, entering the objective lens.

Optical pickup apparatus employing an adjusting circuit

A grating surface of a diffraction grating diffracts a laser beam emitted from a semiconductor laser device in &plusmn;1st order directions. The grating surface is formed in a rectangular or elliptic shape in such dimensions that a light spot formed on an objective lens by &plusmn;1st order diffracted beams is located in an aperture of the objective lens and not displaced from the aperture even if the objective lens is horizontally moved in a tracking operation. A grating surface of another diffraction grating has a width smaller than the width of an overlap region of a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the &plus;1st direction, entering an objective lens and a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the &minus;1st direction, entering the objective lens.

Optical pickup apparatus capable of suppressing offset of a tracking error signal

First and second photodiodes are arranged on the upper surface of a stem, returned light beams diffracted in the &plus; 1st order by a transmission type holographic optical element are received by the first photodiode, while returned light beams diffracted in the &minus; 1st order are received by the second photodiode. The first photodiode has a plurality of light receiving regions, and respectively outputs a reproducing signal, a focus error signal and a tracking error signal on the basis of the returned light beams. On the other hand, the second photodiode has a single light receiving region, and outputs a reproducing signal on the basis of the returned light beams.

Optical pickup apparatus and optical recording medium drive employing the same including a first photo receiving element for detecting the state of light beam and a second photo receiving element for reproducing information

A transmission-type holographic optical element has a four-segment holographic surface divided into four regions of equal areas by virtual dividing lines which are perpendicular to each other. The first dividing line is at an angle with respect to the track direction of an optical disk and the second dividing line is at an angle with respect to the radial direction of the optical disk before tracking phase adjustment. The first dividing line coincides with the track direction of the optical disk and the second dividing line coincides with the radial direction of the optical disk after tracking phase adjustment. A four-segment photodetection part is divided into four photodetection parts of equal areas by a dividing line substantially parallel to the radial direction of the optical disk and a dividing line perpendicular thereto. Parts of a main beam diffracted in two regions located on first diagonal positions of the four-segment holographic surface are condensed as condensed spots on adjacent positions of the first dividing line of the four-segment photodetection part on opposite sides, and parts of the main beam diffracted in the remaining two regions located on second diagonal positions are condensed as condensed spots on separate positions of the second dividing line of the four-segment photodetection part on opposite sides.

Optical pickup apparatus and optical recording medium drive employing

An optical pickup device has a case constructed by joining a lower frame member and an upper frame member. A semiconductor laser device, a three-beam generating diffraction grating, a transmission type holographic optical element, and a reflecting mirror are arranged in the lower frame member. A lead frame is arranged in the lower frame member. The semiconductor laser device is arranged on the lead frame through a heat sink, to emit laser light in a horizontal direction. A photodiode and the lead frame are arranged in the upper frame member. The photodiode has a light receiving surface parallel to the direction of light emission from the semiconductor laser device, and is mounted on the lead frame. The laser light emitted from the semiconductor laser device passes through the three-beam generating diffraction grating and the transmission type holographic optical element, and is then bent upward and introduced into an optical recording medium. Returned light reflected from a recording surface of the optical recording medium is changed in a direction parallel to the direction of light emission from the semiconductor laser device, passes through the transmission type holographic optical element and the three-beam generating diffraction grating again, is then changed vertically upward by the reflecting mirror, and is incident on the photodiode.

Optical pickup device and optical recording medium driving apparatus

A field effect semiconductor device includes an undoped In.sub.0.2 Ga.sub.0.8 As first low-noise drift layer, an undoped In.sub.x Ga.sub.1-x As (x=0.2-0) second low-noise drift layer and an n-type GaAs high-power drift layer in this order. The high-power drift layer includes a first high-power drift layer doped with n-type carrier at high concentration and a second high-power drift layer doped with n-type carrier at low concentration.

Field effect semiconductor device with a low-noise drift layer and a

An undoped Al.sub.0.22 Ga.sub.0.78 As layer, an undoped In.sub.0.2 Ga.sub.0.8 As electron-drifting layer, and an undoped GaAs electron-supplying layer are formed in order on a GaAs substrate. An impurity-doped layer .delta.-doped with Si donor is formed in the GaAs electron-supplying layer. An n-Al.sub.0.22 Ga.sub.0.78 As layer and n.sup.+ -GaAs cap layers are formed in order on the GaAs electron-supplying layer. A source electrode and a drain electrode are formed on the n.sup.+ -GaAs cap layers and a gate electrode is formed on the n-Al.sub.0.22 Ga.sub.0.78 As layer.

Field-effect semiconductor device having heterojunction

A optical divider equally divides a optical carrier into first and second optical carriers. A 180.degree. divider divides an RF sub-carrier signal into first and second RF sub-carrier signals whose phases are 180.degree. inverted from each other. An electro-optic modulator modulates the first optical carrier with the first RF sub-carrier signal and outputs a first optical signal. An electro-optic modulator modulates the second optical signal with the second RF sub-carrier signal and outputs a second optical signal. Photodiodes convert the first and second optical signals transmitted by the optical fibers into first and second electric signals, respectively. A 180.degree. combiner inverts by 180.degree. the phase of the first electric signal and combines it with the second electric signal.

Optical modulation device and fiber optic communication system

A field effect semiconductor device comprises a first channel layer composed of an undoped semiconductor in which electrons mainly drift in low-noise operation and a second channel layer composed of a semiconductor of one conductivity type in which electrons mainly drift in high-power operation, a third channel layer being provided in the second channel layer or on the second channel layer on the opposite side of the first channel layer. The third channel layer is constituted by at least one semiconductor layer of the one conductivity type or undoped having a greater electron affinity than that of the second channel layer and having a smaller forbidden bandgap than that of the second channel layer. In another field effect semiconductor device, an undoped impurity diffusion preventing layer having an electron affinity approximately equal to that of the second channel layer is provided between the first channel layer and the second channel layer.

Field effect semiconductor device

A novel field-effect semiconductor device having both low-noise and high-output operating characteristics has a first semiconductor buffer layer, an undoped second semi-conductor layer, an undoped third semiconductor layer the forbidden band gap of which increases from the substrate to the electrode side, a fourth semiconductor layer of one conductivity type, and a fifth semiconductor layer of undoped type or one conductivity type, formed one on top of another in this order on a semiconductor substrate. When the gate potential is deep, electrons mostly travel through the undoped second and third semiconductor layers, the device exhibiting superior low-noise characteristic; when the gate potential is shallow, electrons mostly travel through the highly doped fourth semiconductor layer, the device thus achieving high output characteristic.

Field-effect semiconductor device

A velocity modulation transistor has a first barrier layer, first channel layer, second barrier layer, second channel layer, third barrier layer, input/output electrode that and control electrode are laminated on a semi-insulative substrate in this order, The electron affinity of the first channel layer is larger than that of the second channel layer. The energy difference between the first level and the second level can be obtained according to the difference in the electron affinity between the first and second channel layers as well as to the control of the film thickness of the first and second channel layers, whereby the velocity modulation effect at room temperature becomes large.

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Yawata, Japan

Minoru Sawada