Abstract: Binary information previously recorded in an innermost rim side area is enabled to be stably reproduced. A record medium is formed by sequentially laminating a first information layer 2, an intermediate layer 3, a second information layer 4, and a cover layer 5 onto a substrate 1. First grooves are previously formed in the innermost rim area of the substrate 1. Second grooves are previously formed in an area where data is recorded. The first grooves are set to be shallower and narrower than the second grooves. Thus, such a situation that a BCA signal is modulated by diffraction due to the grooves can be reduced.

Abstract: Binary information previously recorded in an innermost rim side area is enabled to be stably reproduced. A record medium is formed by sequentially laminating a first information layer 2, an intermediate layer 3, a second information layer 4, and a cover layer 5 onto a substrate 1. First grooves are previously formed in the innermost rim area of the substrate 1. Second grooves are previously formed in an area where data is recorded. The first grooves are set to be shallower and narrower than the second grooves. Thus, such a situation that a BCA signal is modulated by diffraction due to the grooves can be reduced.

Abstract: The stable reproduction of wobble signal without generating beats despite of an improvement in recording density by narrowing a track pitch is realized. Data by magnetooptical recording is recorded on wobbling grooves and lands between adjacent wobbling grooves. The wobbling grooves are provided to wobble both sides of the grooves in different amplitudes. Further, both the sides wobbled in different amplitudes are wobbled in phase in the track direction. These different amplitudes of both sides are preferably set to 3.3 to 40%.

Abstract: The stable reproduction of wobble signal without generating beats despite of an improvement in recording density by narrowing a track pitch is realized. Data by magnetooptical recording is recorded on wobbling grooves (71) and lands (72) between adjacent wobbling grooves (71). The wobbling grooves (71) are provided to wobble both sides of the grooves in different amplitudes. Further, both the sides wobbled in different amplitudes are wobbled in phase in the track direction. These different amplitudes of both sides are preferably set to 3.3 to 40%.

Abstract: In an optical recording medium having a writable area in which grooves are formed along recording tracks and a read-only area in which pits are formed along the recording tracks, sufficient levels of signals required for data write and read can be assured even with the track pitch reduced for a higher recording density. Assuming that the refractive index of a medium provided extending from a light-incident surface to a surface in which the grooves and pits are formed is n and the wavelength of a light used for data write and read is &lgr;, the grooves and pits has a width within a range of &lgr;/7.5 n to &lgr;/6. On the assumption that the width of each of the grooves formed in the writable area is Wg and the pitch between the recording tracks in the writable area is Tp1, Wg/Tp1 is within a range of 18.4% to 31.1%. When it is assumed that the width of each of the pitches formed in the read-only area is Wp and the pitch between the recording tracks in the read-only area is Tp2, Wp/Tp2 is within a range of 35.

Abstract: In an optical recording medium having formed along recording tracks thereon pits indicative of information signal, a ratio Pw/Tp where Pw is the width of the pit and Tp is the pitch of the tracks is within a range of 0.4 to 0.55. The push-pull method or differential push-pull method is adopted for tracking servo control of the optical recording medium.

Abstract: Even if grooves are, in order to improve productivity, omitted from an optical recording medium having pits indicating information signals formed in at least a portion of recording tracks of the optical recording medium, signals having satisfactorily high levels required to perform tracking control are attempted to be obtained. The number of regions of the recording tracks in which the pits are formed is made to be larger than the number of regions in which no pit is formed. Specifically, since "0" has higher appearance probability than "1" in a case of a binary information signal consisting of "0" and "1", pits are formed at positions corresponding to "0" of the information signal.

Abstract: An optical recording medium capable of being reproduced by a conventional drive device which meets an optical disk having grooves and no groove in an area in which pits are formed. In the optical recording medium having pits 1 showing information signals in the shape of protruding and recessed parts, it is assumed that the depth t1 of the above mentioned pits t2 of the pits 1 is located within a range of 0.3 to 0.6 .mu.m. Herein, n designates the refractive index of the base of the optical recording medium and designates the wavelength of the light used for reproduction.

Abstract: A stamper for manufacturing a base of an optical disc where grooves having a track pitch of 1.6 .mu.m and width of 1.3 .mu.m or less are formed by using synthetic resin material includes a plurality of projections for forming grooves and a plurality of recessed portions. The plurality of projections have a flat upper portion and a pair of rising portions provided on the both sides of the upper surface portion. The plurality of recessed portions are formed so that bottom surfaces provided continuously to the rising portions of the respective projections become flat. In this case, when width dimension of the rising portion is .epsilon./2, width .epsilon./2 of the rising portion is given by the following expression:0.05 .mu.m.ltoreq..epsilon./2.ltoreq.0.15 .mu.

Abstract: A method for measuring a deviation between the centerline between grooves defined on both sides of a recording track of an optical disc of a sample servo tracking system and a control prepit pattern formed on the disc is disclosed. If the modulation indices of the wobbled pits are measured under continuous tracking control of the center region or land, a difference is produced in the modulation indices when there is a deviation between the center of the wobbled pits and the center of the grooves. If, under tracking control of the grooves, the tracking offset is adjusted so that the modulation indices of the wobbled pits are equal to each other, the tracking error signal has an offset quantity (DC component). A light beam is swept under tracking control of the land between the grooves and the deviation between the center of the grooves and the control prepit pattern is measured.

Abstract: At the boundary between the program area and the recording area, buffering areas where no valid data exists are respectively provided in the program area and the recording area. These respective buffering areas are caused to be access inhibit area, and neither recording or reproduction is carried out in these areas. For this reason, oscillation of the tracking servo which is likely to take place when light spot is passed through the boundary between the program area and the recording area is suppressed to realize tracking servo stable at all times. Thus, temporary missing of information signals is prevented.

Abstract: An editing can be made in real time while data is being input.

Abstract: A rotation of an optical disk can be controlled with high accuracy to thereby reduce a rotational jitter, whereby a buffer area between sectors can be reduced to increase a storage capacity of the optical disk. In an optical disk in which a track (3) defined by a groove (2) is formed on a rotational base plate and a recording pit (4) corresponding to information is formed on the track (3) in a multi-channel fashion, the groove (2) is formed as a pattern which is fine wobbled in the optical disk radiation direction shown by an arrow (r) and address information (9) of the track (3) is provided in the groove (2).