Matsushita Electric Industrial Co., Ltd.

Tomio Yoshida

Isao Satoh

Kenji Koishi

Shunji Ohara

Shunji Harigae

Michiyoshi Nagashima

Nobuo Akahira

Yoshinobu Nakata

Makoto Ichinose

Yuzuru Kuroki

Noboru Wakami

Tadaoki Yamashita

Shinji Kubota

Kazutoyo Hirosawa

Toshio Sato

Takashi Ishida

Noboru Yamada

Kenichi Nishiuchi

Takeo Ohta

Suzushi Kimura

Tsunenori Yoshida

Sueki Baba

Munehiro Tabata

Tadashi Kawamata

Toshio Satoh

A method and an apparatus for recording information signals on an optical information recording medium which is reversibly changeable between optically distinguishable states corresponding to an irradiating condition of a bundle of high density energy such as laser beam. The starting point of recording signals is randomly changed, and the thermal history of the recording material by the beam irradiation is averaged and the number of repetition recording times is improved. A delay circuit is provided, and reference recording gate signals are formed on the basis of format signals obtained from a recording medium, and a random delay time is set just thereafter, and the starting point of recording of recording signals is started.

Method and apparatus for timing variable optical information recording

An angular velocity sensor includes a pair of vibratory piezoelectric detecting elements defining detecting planes which are disposed in symmetry about a plane containing the sense axis and out of right-angled orientation with respect to this plane. The detecting elements thus arranged assume a widely spread or flattened V-shaped configuration as viewed from above. Output signals of opposite polarities received from the respective detecting elements are weighted respectively and added together so as to cancel out unwanted leak component signals. Thus, leak component signals resulting from assembling tolerances can be canceled. In this instance, if the characteristics of two sensor elements each including one of the detecting elements are fully equivalent, a leak component signal dependent on a disturbing inertial force can simultaneously be canceled out. With this construction, the variation of the offset voltage can be reduced even when the sensor is subjected to a great change in environmental conditions including temperature.

Angular velocity sensor and a sensor apparatus incorporating the same

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.

Optical disk having an index mark

An optical disk apparatus is disclosed in which data is recorded, reproduced and erased on an erasable optical disk. After first data is recorded in a predetermined track or sector, it is erased. Second data is then recorded in the same track or sector, and it is decided that the erase function is normal when the second data is reproduced correctly.

Optical disk apparatus with an erase checking function

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.

Abnormal track skipping detection and control arrangement

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. Moreover, a tracking servo control signal is obtained from the difference between the respective outputs of the peripheral portions among the divided photodetector portions.

Optical head

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).

Optical recording and playback apparatus using plural light spots

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.

Optical recording and reproducing head

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. The portion of the recording medium scanned by the erasing beam spot is scanned by the recording beam spot so that the erasing and recording are carried out substantially simultaneously.

Optical recording and reproducing apparatus having erasing beam spot

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.

Optical and reversible recording and reproducing apparatus

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.

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. The comparator generates a coincidence output signal which prohibits any output from the recording light beam, thus preventing any recording until the next sector on the disc is encountered.

Optical data recording and reproducing apparatus

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. A new directory for a renewed information, which is written in unused region in the same manner as the above, is written so that the renewed information can be read out by using the new directory. When reproducing, an envelope of the reproduced signal is detected to see whether information can be read out or not. Thus, erased information is skipped to reproduce only unerased information.

Method and apparatus for optically recording and reproducing information

The disclosure is directed to an optical recording and reproducing disc in which each track circumference of guide tracks formed into a concentric or spiral configuration is divided into a plurality of sectors for selective recording and reproduction of information in any desired sectors. Sector separating zones of predetermined configuration are provided at starting portions of the respective sectors, while predetermined sector marks indicating the sector separating zones are formed on an index track provided at an outer or inner periphery of the disc in positions corresponding to the sector separating zones so that, during selection of the sectors at recording and reproduction, reproduction signals by the sector marks are used for selection of the sectors, while starting of the recording and reproduction is effected by the reproduced information of the sector separating zones.

Optical having index mark and sector mark

A modulation and demodulation system for an optical data recording and reproducing apparatus is disclosed in which, in an optical disc having an optical guide track and capable of recording and reproducing optically, the guide track is divided into a plurality of data sectors and the recording or reproduction or reading is effected by data sector. The modulation system for the data field for recording the data is different from that for the identification field containing identification data such as a track address and a sector address in such a way that the identification field is reproduced at high reliability and high demodulation speed while at the same time recording data at high density in the data field.

Growing community of inventors

Katano, Japan

Tomio Yoshida