Abstract: A beam is emitted from a radiation source such as a semiconductor laser and is converted to parallel light by a collimator lens. The light enters a surface A of a prism at an incidence angle &phgr; (an angle between the normal line of the surface A and the incident light), thus obtaining light refracted at a refraction angle &psgr; (an angle between the normal line and the refracted light). This refracted light is incident on the surface B of the prism to be reflected totally from this surface, and the reflected light is incident on the surface C of the prism. Then, the reflected light enters the surface B of the prism again and is transmitted through this surface. The transmitted light is converted to convergent light by an objective lens. The convergent light is transmitted through a surface of an optical disk substrate, thus being focused on a signal surface. An optical disk device that is thin beyond the physical limitations without changing the working distance and the numerical aperture can be obtained.

Abstract: In an optical head, two object lenses 3a, 3b fixed to a lens holder 4 are provided to serve as means for condensing a light beam 11 wherein these object lenses 3a, 3b are at positions eccentric from a support axis 10. The object lenses 3a and 3b are fabricated to satisfy prescribed conditions to suppress aberration. When either object lens 3a or 3b is selected for an optical recording medium 17, 18, degrading of signals can be prevented. Alternatively, two light sources 14, 25 are provided for one object lens 19, and the object lens is fabricated to satisfy prescribed conditions to suppress aberration. When either one of the light sources is used, degrading of signals can be prevented. In a different optical head, a recording medium 107 is set on a disk driving device 111, and an optical head 115 is provided movable freely in radial directions. The tilt of the recording medium is detected with a sensor, and the optical axis of the beam is controlled according to the detected tilt to cancel aberration.

Abstract: A prism includes: a first portion made of a first material having a wavelength dependency in a refractive index; and a second portion adhered to the first portion, the second portion being made of a second material having a wavelength dependency in a refractive index which is different from the wavelength dependency in the refractive index of the first material. The first portion and the second portion have shapes such that the wavelength dependency in the refractive index of the first portion and the wavelength dependency in the refractive index of the second portion are substantially cancelled by each other.

Abstract: In an optical recording and reproducing apparatus, two light sources such as a laser diode of different wavelengths from each other are provided, and photosensors receive the light emitted by the light sources and reflected by the optical recording medium. Before recording or reproduction is started, the type of optical recording medium having a different wavelength dependent reflectance is discriminated. Because two wavelengths are used, the difference of the outputs is large, and the type of the optical recording medium is discriminated reliably according to the outputs of the photosensors. Then, the operation of the apparatus is stabilized according to the type of the optical recording medium by optimizing the laser power, the gain of the controller, the revolution number of the medium or the like.

Abstract: In the system of an optical head which conducts recording, reproducing and erasing, etc. on an optical disk by an optical means, the light from an optical disk is guided to photosensors through a diffraction element comprising of two kinds of diffraction gratings, viz. a first and a second diffraction gratings, each made of a partial area of respective zone plates, disposed approximately rectangular to each other; and then, the SSD method focusing error signal is provided from a diffracted light comming from one of the diffraction gratings, while the Far-Field method tracking error signal from the other diffracted light comming from the remaining diffraction grating; thereby a compact high-performance optical head is implemented at low cost.

Abstract: A light beam emitted from a semiconductor laser element is collimated by a collimating lens, and is applied to an optical disk through a polarizing holographic beam splitter, a .lambda./4 plate and an objective lens, a light beam reflected by the optical disk is applied to the polarizing holographic beam splitter and is diffracted. Diffracted light beams of +1st order and -1st order are applied to two photodetectors, and a focus error signal is obtained on the basis of the diffracted light beam of +1st order and a tracking error signal is obtained on the basis of the diffracted light beam of -1st order.

Abstract: A light beam emitted from a semiconductor laser element is collimated by a collimating lens, and is applied to an optical disk through a polarizing holographic beam splitter, a .lambda./4 plate and an objective lens, a light beam reflected by the optical disk is applied to the polarizing holographic beam splitter and is diffracted. Diffracted light beams of +1st order and -1st order are applied to two photodetectors, and a focus error signal and a tracking error signal are obtained on the basis of the diffracted light beam of +1st order and an information signal is obtained on the basis of the diffracted light beam of -1st order.

Abstract: An optical head device includes: a light source for emitting a light beam; an objective lens for converging the light beam on an information storage medium; a hologram for receiving the light beam reflected by the information storage medium and generating diffracted light from the light beam, the hologram having such a polarization anisotropy that it diffracts light in a second polarization state more strongly than light in a first polarization state which is different from the second polarization state; and a photodetector including a plurality of photodetective sections for receiving a part of the diffracted light and outputting a photocurrent in accordance with the intensity of the part of the diffracted light.

Abstract: Disclosed is a compact optical pick-up head apparatus suitable for mass-production, which comprises a light radiation source, an element composed of photodetector split into a plurality of regions and integrated on the same base, an objective lens for focusing a beam from the above source on an optical disk, a blazed hologram integrated to the support member of the lens, a means for driving the support member to which the objective lens and blazed hologram are integrated in response to an output as servo signal output from the photodetector which receives a diffracted beam produced in such a manner that a return beam reflected or diffracted by the optical disk is incident on the objective lens integrated with the above hologram.

Abstract: Optical-beam 2 emitted from semiconductor laser device 1 is transformed into parallel-light 4 by means of collimator lens 3, and a part of parallel-light 4 passed through parallel glass-plate 7 of which the front-surface is mirror finished and the rear-surface is frost finished is inputted into detector 5 monitoring the light-quantity. The optical-beam reflected from parallel glass-plate 7 is focused on information medium 9 after it passed through a collimator-lens 6. The optical-beam reflected from information medium 9 is then introduced on a detector disposed on the semiconductor laser device taking an reversed course. Since no interference of light transmitted through detector 5 is generated in this optical head, a higher linearity of the output of detector 5 can be obtained so that the better stabilized output control of semiconductor laser device 1 by means of laser control circuit 11 can be obtained.

Abstract: An optical head with a polarized beam hologram for optically recording and reproducing information on and from a recording medium. The optical head comprises an optical lens for converging a light beam emitted from a light source on the recording medium and a beam splitter provided between the light source and the optical lens for branching a light beam reflected from the recording medium. Also included in the optical head is a polarization type hologram for causing transmission or reflection of the light beam branched by the beam splitter and for polarizing the light beam so that a 0 order light and a + first-order diffracted light produced due to the polarization are cross polarized with respect to each other and the 0 order light and a - first-order diffracted light produced due to the polarization are cross polarized with respect to each other. The 0 order light, the + first-order diffracted light and the - first-order diffracted light from the hologram are respectively received by photodetectors.

Abstract: An optical head comprises a fixed optical casing and a movable optical casing accommodating a deflecting mirror and an objective lens which moves separately from the deflecting mirror. Windows are inserted in the boundary between the interior and exterior of an optical path to cover a light-exposed area of an optical system so as to prevent dust from entering into the optical casings. Each window is simple in its construction and makes a slight angle with a plane perpendicular to the optical axis of the optical system so that the windows do not become dusty. Each window can be coated with a conductive thin film which is grounded through a conductive area of each optical casing.

Abstract: An optical head system for optically recording and reproducing information on and from an optical recording medium. The optical head system comprises a light source for emitting a light beam, a collimator lens for causing the light beam from the light source means to become a parallel light beam, and an objective lens for converging the parallel light beam from the collimator lens on the optical recording medium. Between said collimator lens and the objective lens is provided a first optical device for reflecting the light beam returning from the optical recording medium. Also included is a second optical device for separating the light beam from the first optical device to generate two light beams, the two separated light beams directing in the substantially same direction and being separated by a predetermined distance from each other. The two separated light beams from said second optical device are separately incident on a photodetector assembly.

Abstract: An optical pickup head for performing recording, reproducing and erasing of information on an optical disc in an optical system employs an objective lens, which is integrated or combined with a holographic optical element, so that the focusing of a diffraction beam on a photo-sensor is stabilized irrespective of the movement of the objective lens due to the tracking control operation in the optical system.

Abstract: An optical head for recording and reproducing information on an optical disk includes a box-like cover carrying thereon a semiconductor laser unit and a detector, and a substantially planar base on which various optical components are bonded, the base being made of the same material as the box-like cover and secured to the box-like cover to close an open end of the latter. By the use of the planar base, the optical components and the base can be bonded efficiently with utmost ease.

Abstract: An optical pickup head apparatus comprises a hologram element disposed in the flux of light reflected back from an optical disc, and first and second photodetectors respectively having linear element boundaries extending in a predetermined direction and disposed so as to receive two-focal-point images on their coplanar detection surfaces, whereby the tolerable width of variation in the light source wavelength and the tolerable range of error in the assembling adjustment of the optics can be extended considerably to permit stable differential signal detection.

Abstract: The combination of recordable-reproduceable optical discs and reproducing-only optical discs and an optical disc player which is capable of reproducing recorded signals both from the recordable-reproduceable optical disc possessing pregrooves and the reproducing-only optical disc possessing recording pits by means of a common optical system. The common optical system has a common laser for irradiating both types of discs with a laser beam used for reading the discs. The wavelength of the laser is .lambda. and the depth or height of the pregrooves of the recordable-reproduceable optical disc is made equal to or less than .lambda./8n, and the depth or height of the recording pits of the reproducing-only optical disc is made equal to or greater than .lambda./8n but less than .lambda./4n, wherein n is the refractive index of the substrate of the disc or the protective layer provided on the surface thereof.

Abstract: An optical device for optically recording and reproducing information in and out of a recording medium. The device consists of a movable optical system which carries out at least two-dimensional movements and a stationary optical system. The movable optical system includes a beam splitter adapted to receive a parallel light beam, an objective lens for focussing the light beam from the second beam splitter onto the medium and a photodetector disposed in the vicinity of the beam splitter and adapted to receive, through the objective lens and the beam splitter, the light beam reflected by the information carrier. The stationary optical system includes a beam splitter for directing the parallel light beam from the source to the beam splitter of the movable optical system and a photodetector for receiving the reflected light beam coming through the beam splitter.

Abstract: An optical information reading device adapted to apply a light beam from a light source to an information carrier having information recorded thereon as convexities and concavities or variations in a light reflecting factor, and to receive the light reflected from the information carrier, thereby to read the information. A specific arrangement of optical elements such as a beam splitter, lens, and reflecting mirror enables the information reading device as a whole to be reduced in size particularly in length in the direction perpendicular to the plane of the information carrier.