摘要:
A digital information recording and reproducing method for significantly improving the transfer rate of digital information, comprises the steps of: forming a plurality of light beam guide tracks on a recording medium capable of multiple light-wavelength recording, the tracks being spaced apart by a predetermined pitch and each of the tracks comprising a series of pre-pits disposed in a scan direction and spaced apart by an interval longer than the diameter of a spot of a light beam for use in recording and reproducing; and recording and reproducing an information bit by changing the light beam to have a different wavelength predetermined n times in a predetermined order while the light beam is scanned by one interval of the pre-pits.
摘要:
An optical detector for detecting at least three optical beams reflected by an optical information recording medium and outputting an electric signal, the optical detector having three light receiving areas each of which receives a respective one of the three optical beams and each of which has four light receiving surfaces, twelve signal lines to transmit an electric signal obtained on respective ones of the four light receiving surfaces of the three light receiving areas, selected ones of the twelve signal lines connected to the four light receiving surfaces of different ones of the three light receiving areas being joined together within the optical detector, and less than nine signal output lines formed by joining the selected ones of the twelve signal lines extend from the optical detector to a signal processing circuit.
摘要:
A bidirectional optical transmission and receiving module of a simplified structure and an optical communication system using the same. The optical transmission and receiving module includes a light emitting device and a light receiving device disposed with in a same package having an opening covered with a cover glass sheet, and a holographic diffraction grating provided on a top or lower surface of the glass sheet. In transmitting operation, a light beam emitted from the light emitting device passes through the diffraction grating to be concentrated onto an end face of an optical fiber by a lens. In receiving operation, a received light beam emanated from the end face of the optical fiber reaches the diffraction grating via the lens to be thereby diffracted. A plus-sign primary diffracted light beam resulting from the diffraction is concentrated onto a light detecting surface of the light receiving device. Signal as transmitted through the optical fiber in the form of signal light can thus be received.
摘要:
A masking type light control layer for decreasing its reflection factor in a high-temperature region is formed on phase pits of an optical disc, and the phase pit depth is set to a predetermined value. A light spot for reproduction is shaped to an elliptical form and two sub-flux beams on the optical disc are spaced by 5/4 track pitch from a principal flux beam in the radial direction of the optical disc. The kind of optical disc is discriminated and reproduction laser power and characteristics of an equalizer circuit are switched in accordance with the type of an optical disc. Through this, a stable servo signal detection can be ensured and repetitive reproduction characteristics can be improved.
摘要:
An information reproducing method for reproducing information recorded on a medium by irradiating a laser beam and detecting a reflected light beam from the medium. The method includes detecting a plurality of reflected light beams in which the polarities of variations in reflected light beam intensity distributions are substantially inverted to each other, the distribution variation being produced when a light spot of the laser beam crosses a track on the medium, generating components of a focus error signal and components of a tracking error signal, adding the components of the focus error signal of the plurality of reflected light beams to generate a focus error signal, and taking a difference between the components of the tracking error signal of the plurality of reflected light beams to generate a tracking error signal.
摘要:
It is desirable to greatly reduce the disturbance that arises in a focusing error signal by a astigmatic detection method and offset that arises in the tracking error signal by a push-pull method when reproducing various information storing disks, such as a DVD-RAM disk. It is also desirable to provide an optical disk apparatus which is able to reproduce a variety of high density optical disks, such as DVD-RAM and DVD-ROM disks, as well as conventional disks, such as CD, CD-ROM, CD-R disks, by using a simple optional head. For this purpose, an optical disk apparatus irradiates three optical beams produced by a diffraction grating on the specified position of an optical disk and detects reflected light using a specified optical detector divided into twelve parts.
摘要:
An optical head eliminates an disturbance which occurs in a focus error signal in association with the decentering of an optical disk when an optical spot crosses a track on a storage film surface, and in addition the optical head cancels an off-set which occurs in a tracking error signal in association with the movement of an objective lens. In the constitution of the optical head, phases of wave surfaces of ±1st order diffracted lights are shifted by an amount of &lgr;/2 with a common period by using a phase-inverted diffraction grating the phase of which is inverted with a period of D &lgr;/(2P . NA) in a radial direction of the optical disk, thus causing, on the optical disk, sub-spots to be located on the same track as a main-spot. Taking advantage of this location, focal point shift error signals of the main-spot and the sub-spots are added to each other with an appropriate gain ratio, thereby making it possible to cancel the disturbance which occurs in the focus error signal. Meanwhile, tracking error signals of the main-spot and the sub-spots according to a push-pull method are subtracted from each other with an appropriate gain ratio, thereby making it possible to cancel the off-set.
摘要:
Disclosed is an optical pickup and an optical disc device using the same, each including a laser diode, a photo-detector having a region divided into at least six photo-detection areas, and a diffraction grating disposed between the laser diode and the photo-detector and having a region divided into four areas by cross-shaped division lines. The diffraction grating divides a light beam reflected from an optical disc into four diffracted light beams. A focus error signal in accordance with a knife edge method and two kinds of tracking error signals in accordance with a push-pull method and a differential phase detection method are detected by irradiating the light beams diffracted at the areas of the diffraction grating on the detection areas of the photo-detector and/or at boundary lines therebetween, and arithmetically operating light intensity signals obtained from the detection areas of the photo-detector. As a result, there can be realized an optical pickup and an optical disc device, each of which can be matched with various optical discs different in structure by detecting a tracking error signal in accordance with the push-pull method and a tracking error signal suitable for a read only disc using only one photo-detector. Further, in the present invention, a holographic element can be used as the diffraction grating.
摘要:
An optical head having a semiconductor laser and a generation of a plurality of reflected light beams from an optical disk which have polarities of intensity distribution variations which are substantially inverted to each other when a periodic structure of the optical disk crosses at least one focused spot on the disk. An optical detection system splits the plurality of reflected light beams and detects the split reflected light beams. An electrical circuit provides a focus error signal of the at least one focused spot and a tracking error signal from the plurality of reflected light beams. The electrical circuit adds focus error signals provides a difference signal between the focus error signals, amplifies tracking error signals with a gain, and obtains a difference between amplified tracking error.
摘要:
Light beam emitted from a laser light source is focused by an objective lens and applied in this state to an optical information recording medium. In the optical path between the laser light source and the objective lens is disposed a diffraction grating inclinedly with respect to the optical axis. This diffraction grating not only reflects the light beam emitted from the laser light source but also separates it into zero order as well as +1st order and -1st order diffracted light beams. Thus, this diffraction grating functions not only as a diffraction grating but also as a mirror. The thus-separated light beams are applied to an optical disc and the reflected light beams from the optical disc are converted to electric signals by means of a photo detector. The .+-.1st order diffracted light beams are used as track servo beams for following the track on the disc. The zero order diffracted light beam is used for reproducing information signals provided from the track on the disc. The diffraction grating has unequally spaced, curvilinear grooves in order to solve the problems of wave front aberration and light spot aberration which are induced by letting the diffraction grating function as both a diffraction grating and a mirror.