Optical recording method using land/groove recording and optcal recording medium therefor

Claim 2

An optical disk recording medium according to claim 1, wherein said address information takes the form of uneven prepits (82) formed in said substrate.

Claim 3

An optical disk recording medium according to claim 2, wherein said address area extends across a plurality of recording tracks in the radial direction of said optical disk recording medium.

Claim 4

An optical disk recording medium according to claim 3, wherein said groove (84) and prepit (82) have the same depth which is 70 nm or less.

Claim 5

An optical disk recording medium according to claim 3, wherein said groove (84) and prepit (82) have the same depth which is 40 nm or more and 60 nm or less.

Claim 6

An optical disk recording medium according to claim 3, wherein said groove (84) and land (85) have substantially the same width which is 0.3 µm or more and 0.75 µm or less.

Claim 7

An optical disk recording medium according to claim 3, wherein said prepit (82) has a minimal diameter which is smaller than the width of each of said groove (84) and land (85).

Claim 8

An optical disk recording medium according to claim 3, wherein said prepit (82) has a minimal diameter which is smaller than the width of each of said groove (84) and land (85), said minimal diameter being in the range of from 0.25 µm to 0.55 µm.

Claim 9

An optical disk recording medium according to claim 1, wherein pieces of said address information (82) are disposed alternately at a period on both sides of an extension of the center line of a groove (84), said period being even times a period at which information recording marks are recorded on said recording track (Fig. 6).

Claim 10

An optical recording method using an optical recording medium (8) in which grooves (84) and lands (85) are formed on a substrate, information recording areas are formed in association with both said groove (84) and said land (85), any groove is not formed but flat address areas are diskretely formed in said information recording area, first and second address pits (82, 831, 832) are disposed in said address area on an extension of the boundary between said groove (84) and said land (85), said first and second address pits being disposed to satisfy such requirements that said first and second address pits are disposed alternately on both sides of an extension of the center line of one groove, that said first and second address pits are disposed alternately on both sides of an extension of the center line of one land, that address pits do not exist on both sides of a position on an extension of the center line of the groove and that address pits do no exist on both sides of a position on an extension of the center line of the land, said method comprising the steps of: irradiating an optical spot on said optical recording medium; detecting a reflected beam from said optical recording medium (8); detecting an address pit (82) from the detected reflected beam to form an address pit readout signal; detecting an address on the basis of the address pit readout signal; sampling and holding an amplitude of a first readout signal obtained from the first address pit of the address pit readout signal; sampling and holding an amplitude of a second readout signal obtained from the first address pit of the address pit readout signal; comparing the amplitudes of the first and second readout signals; forming an offset signal on the basis of a result of comparison; and controlling the irradiation position of the optical spot on the basis of the offset signal (Fig. 4).

Claim 11

An optical recording method according to claim 10, wherein upon detection of a reflected beam from said optical recording medium, a tracking servo signal is formed by detecting a light beam diffracted by a groove by means of a plurality of photodetectors, comparing diffracted beams detected by said plurality of photodetectors and detecting the relative positional relation between said groove and said optical spot, the tracking servo signal is corrected with an offset signal, and the irradiation position of said optical spot is controlled on the basis of the corrected tracking servo signal.

Claim 12

An optical recording/reproducing apparatus using an optical recording medium (8) in which grooves (84) and lands (85) are formed on a substrate, information recording areas are formed in association with both said groove (84) and said land (85), and prepits (84) are disposed on a virtual extension of the boundary between a groove (84) and a land (85), said prepits (82) being disposed to satisfy such requirements that said prepits (82) are disposed on both sides of a virtual extension of the center line of a groove, that said prepits are disposed on both sides of a virtual extension of the center line of a land, that said prepits do not exist on both sides of a position on the center line of the groove, and that said prepits do not exist on both sides of a position on the center line of the land, said apparatus comprising: a light source (311); an optical system (312, 324, 321) for focusing and irradiating a light beam generated by said light source (311) on said optical recording medium (8) in the form of an optical spot (21); photodetectors (333, 334) for detecting a reflected beam from said optical recording medium (8); reproduction means for reproducing information by using signals from said photodetectors (333, 334); a position control circuit (6) for moving the position of an optical spot (21) irradiated by said optical system to a desired position on said optical recording medium (8); an address decode circuit (431) for detecting an address on the basis of a readout signal from said prepit (82) obtained from said photodetectors; means (941) for detecting an amplitude of the readout signal from said prepit (82); means (41) for holding said amplitude; and comparison means (42) for comparing a detected amplitude with the held amplitude, whereby said scanning means (6) is controlled on the basis of an output of said comparison means (42) to control the position of said optical spot (21).

Claim 13

An optical recording/reproducing apparatus using an optical recording medium in which grooves and lands are formed on a substrate, information recording areas are formed in association with both said groove and said land, and prepits are disposed on a virtual extension of the boundary between a groove and a land, said prepits being disposed to satisfy such requirements that said prepits are disposed on both sides of a virtual extension of the center line of a groove, that said prepits are disposed on both sides of a virtual extension of the center line of a land, that said prepits do not exist on both sides of a position on the center line of the groove, and that said prepits do not exist on both sides of a position on the center line of the land, and having light beam generation means, beam focusing means for focusing and irradiating a light beam generated by said light beam generation means on said optical recording medium, photodetection means for detecting a reflected beam of the light beam irradiated by said beam focusing means, reproduction means for reproducing information by using a signal from said photodetection means, and scanning means for moving the position of an optical spot irradiated by said beam focusing means to a desired position on said optical recording medium, said apparatus comprising: means for detecting an address on the basis of a readout signal from a prepit; a low-pass filter for detecting an amplitude of a low frequency component of the readout signal from said prepit; and means for performing lock-in detection of a passed signal of said low-pass filter, whereby the position of the optical spot is controlled on the basis of the detected signal (Fig. 8).

Claim 14

An optical recording medium comprising: a substrate in the form of a circular disk; substantially concentric grooves (84) and lands (85) formed on said substrate; information recording areas formed in association with both said groove (84) and said land (85); and prepits (82) disposed on a virtual extension of the boundary between a groove (84) and a land (85), said prepits being disposed to satisfy all of the following requirements: (i) said prepits are on both sides of an extension of the center line of one groove (84), (ii) said prepits are on both sides of an extension of the center line of one land (85), (iii) said prepits do not exist on both sides of a position on an extension of the center line of one groove (84), and (iv) said prepits do not exist on both sides of a position on an extension of the center line of one land (85).