Abstract: An optical disk is provided which includes a rewritable first recording area and a read-only second recording area. The first recording area includes groove tracks and land tracks divided into first sectors. Each first sector has a header region with identification data and a data region for recording user data. The second recording area includes tracks formed with physical bit rows, the tracks being divided into second sectors. Each second sector includes a header region and a data region having read-only data recorded as the bit rows. The header regions in the first sectors include pits the width of groove tracks and wobbled from a center line of the groove track. The header regions in the second sectors include pits having a width smaller than the groove tracks and formed along the center line of a track.

Abstract: An optical disc using a single-spiral land and groove track format and an address signal enabling simple sector address management and format compatibility with read-only optical disc media is disclosed. Four physical address areas PID1-PID4 are recorded to a header area such that PID1 and PID2 are offset one-half track pitch toward the outside circumference of the disc from the groove track center, and PID3 and PID4 are offset one-half track pitch toward the inside circumference of the disc from the groove track center, and the header area is shared by groove track sectors and land track sectors. A groove track sector address is written to PID3 and PID4, and the sector address of the land track sector adjacent on the outside circumference side of that groove sector is written to PID1 and PID2. The address of each sector increases 1 in the same sequence as the sectors are formed in the recording spiral.

Abstract: A read-only zone or control zone is formed in an optical information recording medium wherein information signal are formed in both grooves and lands. Grooves are not formed in the control zone or read-only zone, and read-only data such as control data, audio-video data, or computer data is pre-recorded as a sequence of pre-formed pits on the track center line. The track pitch of the pre-formed pit sequences in the control zone or read-only zone is equal to the groove pitch in the read-write zones.

Abstract: An optical disk of the present invention has one or more recording tracks formed concentrically or spirally on the disk to which data signals are recorded by forming different-length marks and spaces on the tracks. An ID signal combining marks and spaces of two or more predetermined lengths approximately equal to the length of the marks and spaces forming the data signals is recorded to the recording tracks within a predetermined disk area, thus creating the ID signal by aligning the marks and spaces in the radial direction and recording the aligned marks and spaces to adjacent tracks in a predetermined radial disk area. Also, a reproduction apparatus for reproducing signals from the optical disk is disclosed.

Abstract: A two-layer optical disk has a first layer of a disk shaped recording medium for storing data and a second layer of a disk shaped recording medium placed over the first layer for storing data. Data blocks A, B, C are stored in the first layer in said order. Similarly, data blocks X, Y, Z are stored in the second layer in said order. When reading the data from the two-layer optical disk, the data blocks are read in the order of A, X, B, Y, C, Z.

Abstract: An optical disc record and playback apparatus is provided in which it is possible to record and play back information on erasable discs, as well as write-once discs. When a disc is first inserted into the record and playback apparatus, data written on a control track of the disc is read to identify whether the disc is erasable or write-once. Optimum record and playback parameters are then set depending upon the type of disc. Another aspect of the invention relates to an optical disc in which data representative of the optical sensitivity of the disc is recorded thereon during manufacture. The data is read by the record and playback apparatus and used to adjust the optical recording power so as to compensate for differences in optical sensitivities of different discs.

Abstract: An optical disk for recording audio and video information in unit of field or sector has a recording format that provides an area for recording all audio information to be recorded in each unit immediately after an area used to set the power of the optical beam to a desired level. Also, an audio and video information recording method using the optical disk having the recording format mentioned above is disclosed. According to this method, after-recording of audio information is made at a desired level of the power of the optical beam.

Abstract: This invention relates to a method of determining the optimal recording power for an optical disk apparatus.

Abstract: An appparatus for preventing an undesirable increase in the gain of an automatic gain control circuit (AGC circuit) when an optical pickup of an optical disc reproducing apparatus performs a track jump operation. A detected signal of an optical pickup is applied to an AGC circuit for equalizing the level of the detected signal. The output of the AGC circuit is detected by an envelope detector and compared with a reference level by a comparator. The output of the comparator is applied to the AGC circuit as a gate signal for holding the gain of the AGC circuit to a predetermined value during tracing of a nonrecorded part of a track. Additionally, a jump signal, which is output from a jump signaling device during a track jump operation of the optical pickup, is applied to the AGC circuit to hold the gain to a predetermined value during a track jump operation.

Abstract: In an optical recording disk having groove-like guide tracks, a rotation index mark is provided to indicate a rotation starting point where the rotation index mark is constructed of a grooved-like phase structure. The rotation index mark may be formed in a track which is located separated from the information recording tracks, and may be detected optically without using a laser light beam. The rotation index mark is used to control the rotation of the disk as well as writing and reading operation of an optical disk recording/reproducing apparatus so that various information, such as video signals, can be accurately recorded and reproduced. In the case of recording digital signals, the guide tracks may be divided into a plurality of sector regions, and sector index marks corresponding to respective sector regions may also be formed together with the rotation index mark. Furthermore, an address index mark indicative of the position of track address region radially formed in the guide tracks may also be added.

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: A track skipping detection and control arrangement for an optical recording and reproducing disc formed with guide tracks for use in an optical information recording and reproducing apparatus. According to the track skipping detection and control arrangement of the present invention, any sudden track skipping which may take place during recording can be instantaneously detected by the track traversing signal so as to reduce the recording power for the prevention of erroneous recording to neighboring tracks. Moreover, by distinguishing the track traversing signal detected during the jumping operation for repeated continuous reproduction of the particular one track of the optical disc having spiral tracks, from the traversing signal due to the track skipping, erroneous recording may be similarly prevented also with respect to the optical disc having the tracks in the spiral configuration.

Abstract: An optical head in which the light emitted from a light source is narrowed to a minute spot of light and applied to a recording medium such as a disk thereby to effect recording and reproduction, or reproduction alone. A focusing plate or prism is provided in the optical path for forming the image of the light reflected from the recording medium. The focusing plate or prism has a first surface which reflects and transmits the reflected light and a second surface which is located closer to the image-forming position than the first surface and reflects the reflected light which is transmitted or reflected by the first surface. The optical head is further provided with a photodetector which is divided into at least two portions which individually receive the light rays which are respectively reflected from the first and second surfaces. A focusing servo control signal is obtained from the difference between the respective outputs of the divided photodetector portions.

Abstract: In an optical recording and playback disc apparatus, two light beams (l, m) are focused by a common focusing lens (108) onto an information track (51) of the optical recording disc, and the focused light means (l, m) form two light spots (L, M), the position thereof being controlled by a first tracking servo loop (115, 116 and 117), and furthermore, one (M) of the light spots is independently controlled from the other light spot (L) by a second tracking servo loop (120, 121 and 122).

Abstract: A light beam emitted from a semiconductor laser passes through optical elements which include a condenser lens, a magnifier prism, and a focussing lens to obtain a substantially circular spot of light on a disc. The magnifier prism is constructed such that only the narrower cross-section of the elliptical light beam emitted from the condenser lens is magnified by the incidence surface of the magnifier prism to obtain a substantially circular light beam. The light beam thus obtained is reflected by the prism so that it becomes substantially perpendicular to the beam emitted from the condenser lens. After reflection by the disc, the light passes through a splitter prism. The splitter prism has a reflecting surface and a transmitting surface which spatially bisect the light beam reflected from the disc, a lens and other components. The bisected portions of the beam fall on a photodetector for focussing control and a photodetector for tracking control.

Abstract: Disclosed is an optical recording and reproducing apparatus having an erasing function. The invention aims at providing a practical apparatus which can effect recording, reproducing and erasing of signals in an erasable recording film by applying laser beams thereto. A substantially circular first fine beam spot is formed by a beam source such as a laser, and an elliptic second beam spot for erasing purposes is formed by another beam source such as a laser, with both beam spots are disposed in close proximity of each other on the same guide track. The erasing beam spot is elongated and has an axis which is tangent to the guide track on the recording medium. The power of intensity profile of the erasing beam spot is so controlled that the highest intensity is obtained at the leading end portion of the erasing beam spot as viewed in the direction of the scan, so that the signal can be erased stably and reliably with minimal erasing power.

Abstract: An optical and reversible recording and reproducing apparatus providing a practical apparatus in which information signals can be recorded, reproduced and erased by irradiating a laser beam and the like on the substrate to be optically recorded. More practically, there is provided such an apparatus wherein two light sources such as lasers having different wavelengths are used, and a first almost circular micro-lightspot is produced by one light source, while a second elliptic light spot having a longitudinal diameter in the tangential direction of a guide track on a disc is produced by the other light source. These first and second light spots are closely irradiated on one and the same guide track of an optical recording disc. The recording and reproducing of the signals are performed using the first light spot while the erasure of the recorded signals can be made by using the second light spot or using both first and second light spots in combination.

Abstract: An optical recording and reproducing head wherein light beams emitted from two light sources are combined and applied to a recording medium and the light beams reflected from the recording medium are drawn out in such a way that they are separated from each other. The wavelengths of the light beams from both light sources are different from each other, i.e., .lambda..sub.1, .lambda..sub.2, and the light beams from the light sources are combined by means of a polarization beam splitter, two quarter wave plates and optical filters, and are then simultaneously focussed by a single focussing lens substantially along the optical axis thereof, thereby allowing microspots of focussed light to be disposed on a disc close to each other. The light beams reflected from the disc are drawn out so as to be completely separated from each other by the polarization beam splitter owing to the difference in polarization direction.

Abstract: An optical data recording and reproducing apparatus for recording digital data in a recording track on an optical recording disc. The apparatus includes a light illuminating unit for condensing an output light beam from a light source and for illuminating the disc, a recording-reproducing unit for recording and reproducing the digital data by a recording light beam and a reproducing light beam from the light illuminating unit, a dropout detecting and inspecting unit, and a recording-prohibited sector detecting unit to produce an output signal identifying a recording-prohibited sector where recording is prohibited responsive to an output signal from the dropout detecting and inspecting unit. The sector address of a recording-prohibited sector is recorded at least until recording of digital data in the recording track on the optical disc is begun. A comparator unit compares the sector address of the recording-prohibited sector with a sector address read continuously from the disc.

Abstract: In an optical disc having a file region and a directory region for carrying various pieces of information or data, one or more designated information can be erased by irradiating a laser light beam on a corresponding region in the file region where the light beam is modulated by a superposing writing signal which may be a d.c. or a predetermined a.c. signal. When it is intended to renew the information, designated information is first read out and stored in an external memory prior to performing superposing writing. Meanwhile, the data is renewed and is then written on an unused region in the file region. The directory of the renewed data region is also written so that the renewed information will be read out by searching the new directory. In another embodiment of the invention, the information in the file region is not erased to renew the same, but its directory is erased by superposing writing.