Abstract: An optical device diffracts incident light with a hologram element 19 and receives the diffracted light with light receiving regions 20A to 29 on a light receiving element 12. The light receiving element 12 separately receives reflected main beams used to read information from an optical disc and reflected sub-beams used for a tracking operation with different ones of the light receiving regions. The light receiving regions to receive the reflected main beams are common irrespective of the wavelengths of the reflected main beams. The light receiving regions to receive the reflected sub-beams are different depending on the wavelengths of the reflected sub-beams. The optical device can record and/or reproduce information signals to and/or from optical discs, which need light sources of different wavelengths, without the influence of unnecessary reflected light from the optical discs or without complicating operation of output signals.

Abstract: An optical device diffracts incident light with a hologram element and receives the diffracted light with light receiving faces 20A to 29 on a light receiving element. Reflected sub-beams used for a tracking operation are received with different ones of the light receiving faces depending on the wavelengths of the reflected sub-beams. When first light receiving faces 22, 23, 26, and 27 are receiving an incident beam of a first wavelength, output signals from the first light receiving faces and output signals from the other light receiving faces 24, 25, 28, and 29 are processed to detect an unnecessary light component. The optical device can record and/or reproduce information signals to and/or from optical discs such as DVDs and CDs which need light sources of different wavelengths, without the influence of unnecessary reflected light from the optical discs or without complicating operation of output signals.

Abstract: In a photo pickup device, a hologram element 13 is divided into eight areas. In operation, the hologram elements adds different lens powers to four diffraction lights forming two pairs of diffraction-light groups. In the photo pickup device, a light receiving element 19 is divided into four areas to receive these diffraction lights. The photo pickup device outputs signals corresponding to four quadrants A, B, C and D forming a reflection light from an optical disc 5, allowing a focus-error signal to be calculated in the same logic as an “astigmatism method”.

Abstract: An optical device diffracts incident light with a hologram element 19 and receives the diffracted light with light receiving regions 20A to 29 on a light receiving element 12. The light receiving element 12 separately receives reflected main beams used to read information from an optical disc and reflected sub-beams used for a tracking operation with different ones of the light receiving regions. The light receiving regions to receive the reflected main beams are common irrespective of the wavelengths of the reflected main beams. The light receiving regions to receive the reflected sub-beams are different depending on the wavelengths of the reflected sub-beams. The optical device can record and/or reproduce information signals to and/or from optical discs, which need light sources of different wavelengths, without the influence of unnecessary reflected light from the optical discs or without complicating operation of output signals.

Abstract: In a photo pickup device, an incident area 30 for a reflection light of a light spot is divided into four areas 30a˜30d by parting lines 31, 32 making axial-symmetrical angles with a direction Y of a projected track on an optical disc. In these areas, the so-divided areas 30a, 30c are formed so as to diffract the light in one or more directions in a range of 90 degrees ±20 degrees to the direction Y and impress misalignment on each diffraction light. In each diffraction light, two focal lines produced due to the astigmatism make approx. 45 degrees with the direction Y of the projected track. Further, the divided areas 30b, 30d are characterized by diffracting the light in one or more directions in a range of 90 degrees ±20 degrees to the direction Y.

Abstract: An optical pickup having a simple structure and that is capable of recording using a plurality of wavelengths is provided, comprising a primary laser light source for emitting a primary laser light having a first wavelength and that is of sufficient power for recording, an integrated device further comprising a secondary laser light source for emitting a secondary laser light having a second wavelength that is longer than the first wavelength and that is of sufficient power for recording as well as light receiving elements for receiving the light of the primary and secondary laser lights, and a polarized light beam splitter having polarization selectivity in respect of the secondary laser light.

Abstract: An optical pickup having a simple structure and that is capable of recording using a plurality of wavelengths is provided, comprising a primary laser light source for emitting a primary laser light having a first wavelength and that is of sufficient power for recording, an integrated device further comprising a secondary laser light source for emitting a secondary laser light having a second wavelength that is longer than the first wavelength and that is of sufficient power for recording as well as light receiving elements for receiving the light of the primary and secondary laser lights, and a polarized light beam splitter having polarization selectivity in respect of the secondary laser light.

Abstract: There is disclosed an optical device in which a first light source for outputting a first wavelength light is apart from a second light source for outputting a second wavelength light by a predetermined distance. An information recording medium is irradiated with the first and second wavelength lights transmitted through a holographic optical element having first and second diffraction areas. The first and second diffraction areas are provided with grating arrangements in which grating axis directions are parallel to each other and grating pitches are different from each other. The first and second wavelength lights reflected by the information recording medium are transmitted through the holographic optical element and diffracted by the first and second diffraction areas.

Abstract: There is disclosed an optical device in which a first light source for outputting a first wavelength light is apart from a second light source for outputting a second wavelength light by a predetermined distance. An information recording medium is irradiated with the first and second wavelength lights transmitted through a holographic optical element having first and second diffraction areas. The first and second diffraction areas are provided with grating arrangements in which grating axis directions are parallel to each other and grating pitches are different from each other. The first and second wavelength lights reflected by the information recording medium are transmitted through the holographic optical element and diffracted by the first and second diffraction areas.

Abstract: There is disclosed an optical device in which a first light source for outputting a first wavelength light is apart from a second light source for outputting a second wavelength light by a predetermined distance. An information recording medium is irradiated with the first and second wavelength lights transmitted through a holographic optical element having first and second diffraction areas. The first and second diffraction areas are provided with grating arrangements in which grating axis directions are parallel to each other and grating pitches are different from each other. The first and second wavelength lights reflected by the information recording medium are transmitted through the holographic optical element and diffracted by the first and second diffraction areas.

Abstract: An optical pickup of this invention includes a first laser beam source having a wave length of 780 nm and a second laser beam source having a second wave length of 650 nm wherein the first laser beam source and the second laser beam source are disposed in the vicinity of each other, emission lights from the first laser beam source and the second laser beam source are emitted along substantially the same optical axis and a reflected light from the information recording medium is returned along the optical axis; the first diffraction grating, the second diffraction grating and the light receiving device substrate are disposed in order, the first diffraction grating is substantially transparent for a wave length of 780 nm and diffracts a wave length of 650 nm, and the second diffraction grating is substantially transparent for a wave length of 650 nm while it diffracts a wave length of 780 nm.

Abstract: There is disclosed an optical device in which a first light source for outputting a first wavelength light is apart from a second light source for outputting a second wavelength light by a predetermined distance. An information recording medium is irradiated with the first and second wavelength lights transmitted through a holographic optical element having first and second diffraction areas. The first and second diffraction areas are provided with grating arrangements in which grating axis directions are parallel to each other and grating pitches are different from each other. The first and second wavelength lights reflected by the information recording medium are transmitted through the holographic optical element and diffracted by the first and second diffraction areas.

Abstract: A point where a first diffraction grating and an incident optical axis intersect is named as first intersection point, lengths from the first intersection point to points where ±primary-order diffracted lights by the first diffraction grating intersect a light receiving plane are named as first-a(1a) optical path length, first-b(1b) optical path length, and an average thereof is named as first average optical path length.

Abstract: A reflected beam 6 is diffracted by regions 7a and 7b of a hologram 71, these diffracted beams are converged or diverged, and ±1-order diffracted beams from each region are received by light-receiving regions 9a+to 9b−arranged apart from the center of the hologram by a distance almost optically equal to the distance between the center point of the hologram and a convergence (focal) point of the 0-order reflected beam. Three signals obtained from three regions of each light-receiving region are calculated to obtain a focus signal, and, at the same time, signals obtained from four regions of each light-receiving region are calculated to obtain a tracking signal, so that, by using both the ±1-order diffracted beams, a focus error signal detected by the SSD method and a tracking error signal detected by the DPD method are simultaneously obtained with high efficiency and high precision.

Abstract: An optical pickup has a semiconductor laser that emits a laser beam to read information recorded on a storage medium. A length of an internal resonator of the semiconductor laser is set so as to satisfy a relationship of L.sub.A /(m+1)N<L<L.sub.A /mN where L.sub.A is a length of an external resonator constituted by a beam outgoing surface of the semiconductor laser and a beam reflecting surface of the storage medium, L the length of the internal resonator, N an effective refractive index with respect to a waveguide in the semiconductor laser, and m a natural number. The length L.sub.A is set so as to satisfy a relationship of mNL<L.sub.A <(m+1)NL.

Abstract: A light beam generated by a laser diode travels straight through a holographic beam splitter and other optical elements without undergoing any optical modifications up to an information storage disk (disc), and a return beam reflected on the disk (disc) surface is diffracted and divided into two beams by the holographic beam splitter. The divided two beams are reflected by mirrors respectively and irradiate photo-detectors respectively. A monitoring beam is generated at the back of the laser diode, and is reflected by an additional mirror and irradiates an additional photodetector.

Abstract: An optical integrated circuit includes a substrate and a thin film formed on the substrate. A waveguide is formed by the thin film. A grating coupler includes a plurality of coupling regions for introducing an incident light beam into the waveguide, and for separating the incident light beam into output light beams propagated in the waveguide in different directions respectively. The output light beams are in a same waveguide mode and have polarization directions perpendicular to each other respectively. Photodetectors are exposed to the output light beams propagated in the waveguide for detecting the output light beams respectively.

Abstract: Tilt error detecting apparatus detects a surface tilt of a disc (26) and produces a tilt-error signal (TE) for servo control of optical pickup which is to follow the surface tilt. The apparatus has a movable portion (B) carrying an objective lens (16) for writing/reading optical information on/from a recording surface (26A) of the disc and a mirror (52) or a semi-transparent mirror (24) movable together with the objective lens, and a stationary portion (A) carrying a light beam source (10, 12, 14, 22, 50) for projecting a detection beam (LC.sub.1) to the recording surface through the mirror. The detection beam is reflected at the mirror like recording surface and forms a reflected beam (LC.sub.2). Aperture is provided on the stationary portion for passing a part of the reflected beam, the partly passed reflected beam is projected on a detector which produces the tilt-error signal depending on a position of a beam spot (LC3) produced thereon by the partly passed reflected beam.

Abstract: There is provided an optical pickup which emits a reading light to an optical disc having a pit in which information is stored and reads the information by means of the 0th order reflected light reflected from the pit and the diffracted light generated on the pit by diffraction effect. The optical pickup comprises a semiconductor laser for generating the reading light, a first photodiode for generatign a first electric signal corresponding to the intensity of the 0th order reflected light incident thereto, a second photodiode for generating a second electric signal corresponding to the intensity of the diffracted light incident thereto, a light focusing and guiding device for focusing the reading light to the pit and guiding the 0th order reflected light to the first photodiode, a light guiding device for guiding the diffracted light to the second photodiode and an operation device for generating an output signal by taking difference between the first and the second electric signals.