Abstract: In a three-dimensional recording and reproducing apparatus having a recording medium including a plurality of recording layers stacked on a substrate and an optical system for converging a light irradiated from the substrate side on each of the plurality of recording layers to three-dimensionally record and reproduce information, the following equation is satisfied:.lambda./4.ltoreq.(1/8/NB)(1 /NB.sup.2 -1)NAF.sup.4 .DELTA.dwhere.lambda.: Wavelength of the light;NB: Refractivity of the substrate;NAF: Numerical aperture of a focus lens for converging a light;.DELTA.d: Positional range in the optical axis direction in which exists a recording layer on which the light is to be converged.A light spot is focused on each layer of the multi-layer structured disc to record and reproduce highly reliable data in a high density.

Abstract: A method and apparatus are disclosed which place a glass blank on a lower mold arranged in an opposed relation to an upper mold, heat these molds and glass blank by an infrared lamp unit or high-frequency coil arranged around the molds and press-mold an optical glass element. In the method and apparatus, the infrared lamp unit or high-frequency coil is supported by a supporting mechanism such that it is movable along a direction in which the mold is moved. In cases where a relative position of the infrared lamp unit or high-frequency coil to the mold varies depending upon the shape and size of such molds or the shape and size of optical glass elements obtained, the infrared lamp or high-frequency coil is adjustably moved relative to the mold by a movable mechanism using a motor or air cylinder as an operation source. By using temperature sensors attached to both the molds, the temperatures of the upper and lower molds are controlled to a corresponding desired level.

Abstract: An information recording medium for suppressing the interferences of bits before and after reproduction and improving the optical resolution with saturable absorber 102 disposed adjacent or in an information recording medium layer 103. The recorded information is detected only from a region having a predetermined optical intensity or more of the focused spot so that minute information bits smaller than the optical resolution can be reproduced to improve the recording density of an optical disk drive drastically.

Abstract: An optical disk head having a short wavelength light source has an aperture diaphragm placed in the course of its focusing optical system which can change its aperture diameter depending on the pit size on an optical disk in order to allow recording on and reproducing from not only a short wavelength optical disk, but also a long wavelength optical disk. The aperture diameter is made larger for the smaller pit size and vice versa, and the light source output is adjusted depending on the aperture diameter so that the light amount coming from the disk surface to a photodetector cannot be changed with the aperture diameter.

Abstract: Disclosed is an optical recording and reproducing apparaus comprising a light source directing a light spot toward a recording medium, a detection system detecting light reflected from the recording medium to derive an electrical signal from the reflected light, an information processing circuit modulating the intensity of the light spot according to writing pulses to record information on the recording medium and using the electrical signal to reproduce information from the recording medium, and a tracking servo circuit carrying out tracking servo operation on the basis of the electrical signal and including an extracting circuit connected to a source of extracting pulses having a pulse width at least equal to the writing pulse width so that writing pulse parts contained in the electrical signal are extracted during recording information, whereby a track offset occurring during information recording can be minimized, and the stability of the tracking servo system can be improved.

Abstract: An optical recording and reproducing system for an optical recording medium on which information pits are disposed in a tracking direction of the optical recording medium along adjacent tracks which are separated from each other by a predetermined gap which is half the diameter of an optical spot radiated onto the optical recording medium for recording and reproducing information using the information pits, thereby providing a high track density. Information on the optical recording medium is reproduced using a low cross-talk method in which an optical detector for detecting a light intensity distribution of the radiated optical spot after impingement on the optical recording medium has a detecting surface divided into first, second, and third detecting areas. The second detecting area is disposed between the first and third detecting areas. The information on the optical recording medium is reproduced using outputs of the first and third detecting areas.

Abstract: In optically coupling a plurality of light sources to an optical system for focusing light beams from the light sources into spots on a record plane, a center axis of a light beam from a first one of the light sources is aligned to an optical axis of the focusing optical system, and the spots other than a first spot formed by the light beam from the first light source are rotated around the first spot on the record plane to position the spots to the respective target tracks, and a tracking error signal for at least one of the first spot and another spot is detected and the positions of the plurality of spots are integrally controlled based on the detected tracking error signal so that the plurality of spots can follow the respective target tracks. The target tracks to which the spots are to be positioned may be either one track or different tracks. The positioning of the spots to the target tracks may be done either manually or automatically.

Abstract: A method and an apparatus for recording and reproducing information for use with an optical disk apparatus in which a pit edge recording method is used. According to the pit edge recording method, the leading edge and the trailing edge of a hole pit or a record domain generated during a recording operation are dealt with as information. During the recording, the recording pulse width and the recording power are corrected, and during the reproduction, the variation in the edge position is corrected.

Abstract: When recording domains are formed locally on a recording medium and information is recorded and reproduced by using rise and fall in a reproduced waveform obtained from the recording domains as data, timing patterns indicating start of demodulation are recorded for the lead-edge and the tail-edge of the recording domains, respectively; time interval between the timing signal for starting demodulation detected from the rise in the reproduced waveform and the timing signal for starting demodulation detected from the fall in the reproduced waveform is detected; time shifts of the signals detected from the lead-edge and the tail-edge of the recording domains succeeding the timing patterns for starting demodulation by using the time interval thus detected; and the information is stably detected as time sequential data having no jitter.

Abstract: Method and apparatus for optically detecting information from a recording medium in which pits are formed by thermal energy of a light spot to record the information. A reproduction spot is irradiated onto the recording medium to produce a detection signal. From a differential signal of the detection signal, a signal indicative of zero points of the differential signal and a signal indicative of the presence of the pits are detected, and both the signals are used to detect positions of the pits. For stable and accurate detection of the pit position, the relation between pit size W and reproduction spot size W.sub.s is prescribed and the pit size and reproduction spot size are so set as to satisfy 0.45.ltoreq.W/W.sub.s .ltoreq.0.75.

Abstract: In an optical recording system wherein the intensity of a laser beam is modulated with an input modulation signal so as to record information on a recording medium, the intensity modulation of the laser beam is performed after the pulse waveform of the input modulation signal is converted into two pulses which express the front edge and rear edge of the pulse waveform respectively.